Row involving stray dog (7)
I believe the answer is:
Here is my best explanation:
'dog' is the definition.
(terrier is a kind of dog)
'row involving stray' is the wordplay.
'row' becomes 'tier' (tier is a kind of row).
'involving' is an insertion indicator.
'stray' becomes 'err' ('err' can be a synonym of 'stray').
'tier' placed around 'err' is 'TERRIER'.
(Other definitions for terrier that I've seen before include "Reserve soldier", "Small lively dog, may be Scotch", "Volunteer", "Small, short-bodied dog", "See 11", "part-timer in Services", "(Yorkshire?) dog", "inventory of property", "Dog - army volunteer - land register" and "Dog - reservist".)