Nick, being married, behaves as he should (14)
I believe the answer is:
misappropriate
'nick' is the definition.
(I've seen this before)
'being married behaves as he should' is the wordplay.
I cannot really understand how this works, but
'being' could be 'pro' (pro is a kind of being) and 'pro' is present in the answer.
'married' could be 'm' (abbreviation, e.g. in genealogy) and 'm' is found within the answer.
'he' could be 'isa' and 'isa' is located in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for misappropriate that I've seen before include "Nick" , "Steal, take unfairly" , "pocket" , "Wrongly assume" , "Take dishonestly for one's own use" .)