Fitting edging for adult coats quietly (3)
I believe the answer is:
apt
'fitting' is the definition.
(both mean appropriate)
'edging for adult coats quietly' is the wordplay.
'edging for' means to remove the middle letters (only the letters at the edges).
'coats' indicates putting letters inside (inserted letters are coated in another word).
'quietly' becomes 'p' (p for piano and quiet).
'adult' with its middle taken out is 'at'.
'at' going around 'p' is 'APT'.
(Other definitions for apt that I've seen before include "Liable" , "Befitting" , "Appropriate for Pat" , "Fitting - inclined" , "Suitable or likely" .)