Row about granny's first cat (5)
I believe the answer is:
tiger
'cat' is the definition.
(tiger is a kind of cat)
'row about granny's first' is the wordplay.
'row' becomes 'tier' (a tier is a row of things).
'about' is an insertion indicator.
'granny's first' becomes 'g' (tst letter of 'granny').
'tier' going around 'g' is 'TIGER'.
(Other definitions for tiger that I've seen before include "Dangerous animal" , "Fierce, determined type" , "Large wild cat" , "Shere Khan's type" , "fierce animal" .)