An abnormal appetite, no argument about that (6)
I believe the answer is:
agreed
'an abnormal appetite no' is the definition.
Both the answer and definition are adjectives. Maybe they are linked in a way I don't understand?
'argument about that' is the wordplay.
I cannot quite understand how this works, but
'about' could be 're' ('re' means regarding or about) and 're' is located in the answer.
The remaining letters 'aged' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for agreed that I've seen before include "Corresponded" , "Tallied - reconciled" , "came to the same conclusion" , "It's a deal!" , "Expressed willingness" .)