Part of the chorus that's followed by foxtrot (4)
I believe the answer is:
echo
'that's followed by foxtrot' is the definition.
(in the NATO Phonetic Alphabet)
'part of the chorus' is the wordplay.
'part of' indicates a hidden word.
'ECHO' is hidden in the letters of 'the chorus'.
(Other definitions for echo that I've seen before include "Before foxtrot" , "copy" , "Return of sound waves" , "repetitive" , "Repetition of sound" .)