Allow a little subtlety? (3)
I believe the answer is:
let
'allow' is the definition.
(synonyms)
'a little subtlety?' is the wordplay.
'a little' indicates a hidden word.
'LET' is hidden in the letters of 'subtlety'.
(Other definitions for let that I've seen before include "Was inclined to ignore" , "Allow - hire" , "Allow or lease" , "inefficient service" , "Allow; leased" .)