Sheep to drive home (3)
I believe the answer is:
ram
I believe this is a double definition.
'sheep' is the first definition.
(male sheep)
'drive home' is the second definition.
(to ram something in is to drive it home)
'to' acts as a link.
(Other definitions for ram that I've seen before include "Computer memory of a sheep?" , "Butter" , "Bump into forcibly" , "Butt" , "Crash into, maybe for battering" .)