Agent in pursuit of man is a criminal (10)
I believe the answer is:
malefactor
'criminal' is the definition.
(thesaurus)
'agent in pursuit of man' is the wordplay.
'agent' becomes 'factor' (business term for a representative).
'in pursuit of' means one lot of letters go next to another.
'man' becomes 'male' (**).
'factor' put after 'male' is 'MALEFACTOR'.
'is a' is the link.
(Other definitions for malefactor that I've seen before include "bad person?" , "One doing wrong" , "culprit?" , "Wrongdoer" , "Criminal, evil-doer" .)