Bird – male – appearing south of river (5)
I believe the answer is:
heron
'bird' is the definition.
(heron is a kind of bird)
'male appearing south of river' is the wordplay.
'male' becomes 'he'.
'appearing' becomes 'on' (e.g. on stage or on television).
'south of' says to put letters next to each other.
'river' becomes 'r'.
'on' after 'r' is 'ron'.
'he'+'ron'='HERON'
(Other definitions for heron that I've seen before include "Large British wading bird" , "Tall wading bird" , "Wading bird with long neck and legs" , "flier" , "Long-legged long-necked wading bird" .)