Herbivorous mammal in attack (4)
I believe the answer is:
goat
This might be a double definition.
'herbivorous mammal' is the first definition.
'goat' can be an answer for 'mammal' (goat is a kind of mammal). I'm not certain of the 'herbivorous' bit.
'attack' is the second definition.
(go at)
'in' is the link.
Can you help me to learn more?
(Other definitions for goat that I've seen before include "foolish person" , "heavenly sign" , "nanny, for example" , "Beast (of Capricorn)" , "Butting nanny, perhaps?" .)