Row about mistake getting small dog (7)
I believe the answer is:
terrier
'small dog' is the definition.
(I've seen this before)
'row about mistake' is the wordplay.
'row' becomes 'tier' (tier is a kind of row).
'about' is an insertion indicator.
'mistake' becomes 'err' ('err' can be a synonym of 'mistake').
'tier' going around 'err' is 'TERRIER'.
'getting' is the link.
(Other definitions for terrier that I've seen before include "(Yorkshire?) dog" , "Small, originally burrowing, dog" , "Small, short-bodied dog" , "Small, active breed of dog" , "Short-bodied canine" .)