A young woman is wrong (5)
I believe the answer is:
amiss
'is wrong' is the definition.
(synonyms)
'a young woman' is the wordplay.
'young woman' becomes 'miss' (title for a young woman).
'a'+'miss'='AMISS'
(Other definitions for amiss that I've seen before include "Faulty" , "Mistakenly" , "Revealing fault" , "Not functioning properly" , "Wrong; inaccurate" .)