Punished for a piece of infidelity, possibly (5)
I believe the answer is:
fined
'punished' is the definition.
(similar in meaning)
'piece of infidelity possibly' is the wordplay.
I cannot quite see how this works, but
'piece' could be 'fin' (fin is a kind of piece) and 'fin' is found in the answer.
The remaining letters 'ed' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
'for a' acts as a link.
Can you help me to learn more?
(Other definitions for fined that I've seen before include "Mulcted" , "Fed in (anag.)" , "Imposed financial penalty on" , "Ordered to pay penalty" .)