Criminal element following stag? (10)
I believe the answer is:
malefactor
'criminal' is the definition.
(I know that criminal can be written as malefactor)
'element following stag?' is the wordplay.
'element' becomes 'factor' (synonyms).
'following' means one lot of letters go next to another.
'stag?' becomes 'male' (a stag is a male deer).
'factor' after 'male' is 'MALEFACTOR'.
(Other definitions for malefactor that I've seen before include "culprit?" , "bad person?" , "Sinner" , "Wrongdoer" , "Criminal, evil-doer" .)