Animal munching a tuber (5)
I believe the answer is:
brute
'animal' is the definition.
(I know that animal can be written as brute)
'munching a tuber' is the wordplay.
'munching' indicates an anagram (letters crushed or munched into a new form).
'tuber' is an anagram of 'BRUTE'.
(Other definitions for brute that I've seen before include "Cruel creature" , "Vicious type" , "'Et tu, - - !' (J.Caesar)" , "Monster" , "Heartless individual" .)