Sharp expressions of disapproval about being stuck in AE (6)
I believe the answer is:
astute
'sharp' is the definition.
(I know that sharp can be written as astute)
'expressions of disapproval about being stuck in ae' is the wordplay.
'expressions of disapproval' becomes 'tuts' (I've seen this in another clue).
'about' says the letters should be written in reverse.
'being stuck in' indicates putting letters inside.
'tuts' back-to-front is 'stut'.
'stut' placed inside 'ae' is 'ASTUTE'.
(Other definitions for astute that I've seen before include "Subtle" , "Clever and canny" , "Having hardheaded intelligence" , "Shrewd, quick to spot advantage" , "Percipient" .)