Charlie feels bitter taking in another's curvy shapes (9)
I believe the answer is:
'curvy shapes' is the definition.
(a crescent is a curved shape)
'charlie feels bitter taking in another's' is the wordplay.
'charlie' becomes 'c' (phonetic alphabet: alpha, bravo, charlie etc.).
'feels bitter' becomes 'resents' (to feel resentful is to feel bitter).
'taking in' is an insertion indicator.
'another's' becomes 'c' (I can't explain this - if you can you should give a lot more credence to this answer).
'resents' enclosing 'c' is 'rescents'.
(Other definitions for crescents that I've seen before include "Parts of a circle, shapes of the moon at certain times" , "bent ways" , "Things shaped like the waxing moon" .)