Outlaw Y chromosome? (10)
I believe the answer is:
malefactor
This clue might be a double definition.
'outlaw' is the first definition.
(thesaurus)
'y chromosome?' is the second definition.
Although both the answer and definition are singular nouns, I cannot see how one could define the other.
(Other definitions for malefactor that I've seen before include "Sinner" , "culprit?" , "bad person?" , "One doing wrong" , "Wrongdoer" .)