Bullocks (6)
I believe the answer is:
steers
'bullocks' is the definition.
('steer' can be a synonym of 'bullock')
This is the entire clue.
(Other definitions for steers that I've seen before include "Guides a ship or car" , "Castrated oxen" , "Guides or pilots" , "Castrated bulls" , "Guides direction of, ship or plane" .)