It's wrong to credit one to me (5)
I believe the answer is:
crime
'it's wrong' is the definition.
(I've seen this before)
'credit one to me' is the wordplay.
'credit' becomes 'cr' (abbreviation).
'one' becomes 'i' (Roman numeral).
'cr'+'i'+'me'='CRIME'
'to' is the link.
(Other definitions for crime that I've seen before include "Illegal act" , "Lawbreaking" , "Unlawful act" , "A serious offence" , "An act punishable by law" .)