The animal, making a row, started growling inside (5)
I believe the answer is:
tiger
'the animal' is the definition.
(tiger is a type of animal)
'a row started growling inside' is the wordplay.
'a row' becomes 'tier' (a tier is a row of things).
'started' suggests taking the first letters.
'inside' is an insertion indicator.
The first letter of 'growling' is 'g'.
'tier' placed around 'g' is 'TIGER'.
'making' acts as a link.
(Other definitions for tiger that I've seen before include "Carnivorous large cat" , "Formidable competitor" , "Predator" , "Dynamo" , "Endangered carnivore" .)