It's wrong for a young girl (5)
I believe the answer is:
amiss
'it's wrong' is the definition.
(synonyms)
'a young girl' is the wordplay.
'young girl' becomes 'miss' (I've seen this before).
'a'+'miss'='AMISS'
'for' is the link.
(Other definitions for amiss that I've seen before include "Not functioning properly" , "error" , "In an inappropriate way" , "astray" , "Fallacious" .)