There's nothing in chap's complaints (5)
I believe the answer is:
moans
'complaints' is the definition.
(I've seen this in another clue)
'there's nothing in chap's' is the wordplay.
'there's nothing' becomes 'o' (I've seen this in other clues).
'in' indicates putting letters inside.
'chap's' becomes 'man's' (chap can mean a man).
'o' inserted inside 'mans' is 'MOANS'.
(Other definitions for moans that I've seen before include "Complains" , "Expressions of unhappiness" , "Grumbles" , "Mournful sounds" , "Trivial complaints" .)