Firm rig confused a dog (5)
I believe the answer is:
corgi
'a dog' is the definition.
(corgi is a kind of dog)
'firm rig confused' is the wordplay.
'firm' becomes 'co' (a firm is a company).
'confused' indicates anagramming the letters.
'rig' with letters rearranged gives 'rgi'.
'co'+'rgi'='CORGI'
(Other definitions for corgi that I've seen before include "pet in 9 [CARDIFF]?" , "Toy car manufacturer" , "Pre-2018 royal dog" , "Queen likes this" , "Dog popular with British royals" .)