Bovine mouthful (3)
I believe the answer is:
cud
'bovine mouthful' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for cud that I've seen before include "It's partly digested and chewed again" , "Re-chewed food of a ruminant" , "THIRD PART OF 23" , "Ruminants chew it (3)" , "Wad of something chewable" .)