Rage at seducer, a bloodsucker (7)
I believe the answer is:
vampire
'a bloodsucker' is the definition.
(I've seen this before)
'rage at seducer' is the wordplay.
'rage' becomes 'ire' (ire is intense rage).
'at' means one lot of letters go next to another (I've seen this in other clues).
'seducer' becomes 'vamp' (I've seen this in another clue).
'ire' put after 'vamp' is 'VAMPIRE'.
(Other definitions for vampire that I've seen before include "Blood-sucker (bat)" , "Transylvanian bloodsucker" , "Type of bat" , "Member of the living dead, drinks blood" , "Blood-sucking ghoul" .)