Row about stray dog (7)
I believe the answer is:
terrier
'dog' is the definition.
(terrier is a kind of dog)
'row about stray' is the wordplay.
'row' becomes 'tier' (a tier is a row of things).
'about' is an insertion indicator.
'stray' becomes 'err' (to err is to stray or go wrong).
'tier' going around 'err' is 'TERRIER'.
(Other definitions for terrier that I've seen before include "Breed of dog - Territorial Army volunteer" , "Small lively dog, may be Scotch" , "Small, short-bodied dog" , "Short-bodied canine" , "Sealyham, for example" .)