Carnivore's length added to value (5)
I believe the answer is:
ratel
'carnivore's' is the definition.
(ratel is a kind of carnivore)
'length added to value' is the wordplay.
'length' becomes 'l' (**).
'added to' is a charade indicator (letters next to each other).
'value' becomes 'rate' ('rate' can be a synonym of 'value').
'l' put after 'rate' is 'RATEL'.
(Other definitions for ratel that I've seen before include "Honey badger" , "one wanting honey" , "creature with sweet tooth" , "Badger-like creature" , "wild animal" .)