Dog bringing back one grand, fabulous bird (5)
I believe the answer is:
corgi
'dog' is the definition.
(corgi is a kind of dog)
'back one grand fabulous bird' is the wordplay.
'back' shows that the letters should be reversed in order.
'one' becomes 'i' (Roman numeral).
'grand' becomes 'g' ('G' can be a synonym of 'grand').
'fabulous bird' becomes 'roc' (I've seen this before).
'i'+'g'+'roc'='igroc'
'igroc' reversed gives 'CORGI'.
'bringing' acts as a link.
(Other definitions for corgi that I've seen before include "The Queen's favourite?" , "Dog of Welsh breed, royal favourite" , "Dog popular with British royals" , "Welsh breed of short-legged dog" , "Queen's dog?" .)