Fabulous bird taken aback by soldier's dog (5)
I believe the answer is:
corgi
'dog' is the definition.
(corgi is a kind of dog)
'fabulous bird taken aback by soldier's' is the wordplay.
'fabulous bird' becomes 'roc' (I've seen this before).
'taken aback' says the letters should be written in reverse.
'by' says to put letters next to each other.
'soldier' becomes 'gi' (government issue or general issue).
'roc' reversed gives 'cor'.
'cor'+'gi'='CORGI'
(Other definitions for corgi that I've seen before include "Pre-2018 royal dog" , "found in the kennels" , "Dog at Buckingham Palace" , "One of the Queen's dogs?" , "Royal canine" .)