Spy something the make-up is trying to conceal? (4)
I believe the answer is:
mole
'spy' is the definition.
(I know that mole is a type of spy)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for mole that I've seen before include "Spy, skin spot and furry animal" , "Counterspy" , "Amount of substance" , "Underground worker!" , "Skin spot; breakwater" .)