Bird on fire - first of ostriches (8)
I believe the answer is:
flamingo
'bird' is the definition.
(flamingo is a kind of bird)
'fire first of ostriches' is the wordplay.
'fire' becomes 'flaming' (synonyms).
'first of ostriches' becomes 'o' (1st letter of 'ostriches').
'flaming'+'o'='FLAMINGO'
'on' acts as a link.
(Other definitions for flamingo that I've seen before include "Pretty bird" , "Tall wading bird" , "Exotic bird" , "Long-legged wader" , "Pink wader" .)