I’m messing with chap? No, many! (12)
I believe the answer is:
nymphomaniac
'i'm messing with chap? no many' is the definition.
I can't judge whether this definition defines the answer.
'i'm messing with chap? no many' is the wordplay.
'messing with' indicates an anagram (I've seen 'mess' mean this).
'chap'+'no'+'many'='chapnomany'
'im' mixed up with 'chapnomany' gives 'NYMPHOMANIAC'.
Can you help me to learn more?
(Other definitions for nymphomaniac that I've seen before include "Woman who loves the other" , "Woman with great sexual appetite" .)