Cud-chewing animal (8)
I believe the answer is:
ruminant
'cud-chewing animal' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for ruminant that I've seen before include "Cud chewer" , "Animal chewing cud" , "One chews the cud" , "contemplating" , "Eg, sheep, giraffe, cow" .)