Be stoical and smart, grinding teeth to tackle bovine animal (4,3,6)
I believe the answer is:
bite the bullet
'be stoical' is the definition.
(I've seen this before)
'smart grinding teeth to tackle bovine animal' is the wordplay.
'smart' becomes 'bite' (biting is a kind of smarting).
'grinding' is an anagram indicator (letters must be ground into a new form).
'to tackle' indicates putting letters inside (tackle can mean to take hold of).
'bovine animal' becomes 'bull' (I've seen this before).
'teeth' with letters rearranged gives 'theet'.
'theet' going around 'bull' is 'thebullet'.
'bite'+'thebullet'='BITE THE BULLET'
'and' is the link.
(Other definitions for bite the bullet that I've seen before include "Commit oneself" , "Grasp the nettle" , "Deal with difficulty" , "Be stoic" , "resign oneself?" .)