Enthuse over northern bird (5)
I believe the answer is:
raven
'bird' is the definition.
(raven is a kind of bird)
'enthuse over northern' is the wordplay.
'enthuse' becomes 'rave'.
'over' is a charade indicator (letters next to each other).
'northern' becomes 'n' (abbreviation e.g. N. Ireland).
'rave'+'n'='RAVEN'
(Other definitions for raven that I've seen before include "Crow-like bird" , "Hungrily devour" , "Jet-black" , "Largest member of crow family" , "flesh-eating bird" .)