Repeat in the choir (4)
I believe the answer is:
echo
'repeat' is the definition.
(I know that repeat can be written as echo)
'in the choir' is the wordplay.
'in' indicates a hidden word.
'ECHO' is hidden within 'the choir'.
(Other definitions for echo that I've seen before include "Say again or imitate" , "Sound heard before" , "one catches on the rebound?" , "next to delta" , "In Roman mythology, the nymph who loved Narcissus" .)