Bird very hot sitting on egg? (8)
I believe the answer is:
flamingo
'bird' is the definition.
(flamingo is a kind of bird)
'very hot sitting on egg?' is the wordplay.
'very hot' becomes 'flaming' (flaming hot).
'sitting on' says to put letters next to each other.
'egg?' becomes 'o' (an 'o' resembles an egg).
'flaming'+'o'='FLAMINGO'
(Other definitions for flamingo that I've seen before include "Wading bird with pink and red plumage" , "Pretty bird" , "Long-legged wader" , "colourful bird" , "Exotic bird" .)