Repeat the choral part (4)
I believe the answer is:
echo
'repeat' is the definition.
(synonyms)
'the choral part' is the wordplay.
'part' says the answer is hidden in the clue.
'ECHO' is hidden within 'the choral'.
(Other definitions for echo that I've seen before include "Return of sound waves" , "Rebounding sound" , "letter we hear" , "Radio operator's word for 'E'" , "Marked by heat" .)