Carnivores good in rows? (6)
I believe the answer is:
tigers
'carnivores' is the definition.
(tiger is a kind of carnivore)
'good in rows?' is the wordplay.
'good' becomes 'g' (abbreviation).
'in' indicates putting letters inside.
'rows?' becomes 'tiers' (tier is a kind of row**).
'g' inserted into 'tiers' is 'TIGERS'.
(Other definitions for tigers that I've seen before include "Large striped felines" , "Large forest felines" , "Large striped cats" , "Great striped animals, poetically burning bright" , "strong economies" .)