Composer given thanks returning stuff (7)
I believe the answer is:
satiate
'stuff' is the definition.
(I know that stuff can be written as satiate)
'composer given thanks returning' is the wordplay.
'composer' becomes 'satie' (French composer Erik Satie).
'given' means one lot of letters goes inside another.
'thanks' becomes 'ta' (UK informal version of 'thank you').
'returning' says the letters should be written in reverse.
'ta' backwards is 'at'.
'satie' going around 'at' is 'SATIATE'.
(Other definitions for satiate that I've seen before include "stuff" , "content" , "Gratify fully" , "Overfill - gorge" , "Completely satisfy" .)