Chap has old complaint (4)
I believe the answer is:
moan
'complaint' is the definition.
(thesaurus)
'chap has old' is the wordplay.
'chap' becomes 'man' (I've seen this before**).
'has' means one lot of letters goes inside another.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'man' going around 'o' is 'MOAN'.
(Other definitions for moan that I've seen before include "Lament; grumble" , "Beef" , "Complain mournfully" , "Complaint" , "Low sound of pain" .)