word - And now you see it

It tickles me that the word TUNA is found within FORTUNATE. And there is a COFFIN in SCOFFING. And who put the LAGER in the VILLAGER? The SKIER in RISKIER? The ROMAN in the MICROMANAGER? The TURBAN in DISTURBANCE? The ONCE in CONCERN? The MEAT in PERMEATE?

These words have always been there. Although I've been looking at them my whole life, I've only just noticed them recently. They were hidden in plain sight!

Maybe you've noticed them before. Let's test your powers of observation on some others.

Example:

Fill in the blanks below with a well-known 5-letter word to complete all the words:
    P_____G
    ST_____G
    DIS_____G



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Answer:  ROBIN

because it completes all the words:

    PROBING
    STROBING
    DISROBING

See how many of the 10 below you can solve.

Super helpful clue: The fill-in word is semantically and etymologically unrelated to the containing words. (Well, almost always.)

1.  Fill in the blanks below with a well-known 4-letter word to complete all the words:
        SI____NES
        MO____NG
        FI____TY



2.  Fill in the blanks below with a well-known 6-letter word to complete all the words:
        S______
        B______
        CA______


3.  Fill in the blanks below with a well-known 6-letter word to complete all the words:
        CH______
        REP______
        IMP______T



4.  Fill in the blanks below with a well-known 5-letter word to complete all the words:
        C_____NG
        G_____NG
        _____T


5.  Fill in the blanks below with a well-known 4-letter word to complete all the words:
        VI____S

        CHO____S
        WAL____S


6.  Fill in the blanks below with a well-known 5-letter word to complete all the words:
        _____RD
        _____UNT
        _____VER



7.  Fill in the blanks below with a well-known 4-letter word to complete all the words:
        ____DS
        L____T
        SE____
        ST____
        S____ESS


8.  Fill in the blanks below with a well-known 6-letter word to complete all the words:
        EX______G

        INS______G
        RES______G


9.  Fill in the blanks below with a well-known 6-letter word to complete all the words:
        PU______S
        FLE______S
        FLA______S



And this one is just too icky not to include:

10.  Fill in the blanks below with a well-known 5-letter word to complete all the words:
        BA_____T
        EA_____T
        HOR_____

NOTE: Problem #2 relies on an obscure word which is often mistaken for a more common word. I am disqualifying it and removing it from consideration. However, you may still try to solve it, if you like.

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Epilogue:

@Randal'Thor and @El-Guest — That was some quick solving! Good work.

Here are more fun facts about these words:

1. DELI is also contained in YODELING, DANDELION, and CHANDELIER

5. RUSE is also contained in UTERUSES and ABSTRUSE

7. AMEN is also contained in ORNAMENT

10. Also AMUSEMENT and CASEMENT

Now be sure to check out the B side here.

Answer

1. 
   

   From me

   
   

   
   

   DELI (sidelines, modeling, fidelity)

   
   

   
   


2. 
   

   From me and Rand al’ Thor, somewhat simultaneously

   
   

   
   
   

   LENDER (slender, blender, calender)

   
   

   
   


3. 
   

   From me

   
   

   
   

   AIRMEN (chairmen, repairmen, impairment)

   
   

   
   


4. 
   
   

   From Rand al’ Thor

   
   

   
   

   RABBI (crabbing, grabbing, rabbit)

   
   

   
   


5. 
   

   From Gareth McCaughan

   
   

   
   

   RUSE (viruses, choruses, walruses)

   
   

   
   
   


6. 
   

   From me

   
   

   
   

   DISCO (discord, discount, discover)

   
   

   
   


7. 
   

   From me

   
   

   
   
   

   AMEN (amens, lament, seamen, stamen, sameness)

   
   

   
   


8. 
   

   From Rand al’ Thor

   
   

   
   

   PECTIN (expecting, inspecting, respecting)

   
   

   
   


9. 
   
   

   From Rand al’ Thor

   
   

   
   

   SHINES (pushiness, flashiness, fleshiness)

   
   

   
   


10. 
    

    From me

    
    

    
    

    SEMEN (basement, easement, horsemen)