Plow-pulling beasts (4)
I believe the answer is:
oxen
'plow-pulling beasts' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for oxen that I've seen before include "Doctored bulls" , "Steers" , "Bovine animals, in yoke" , "Lowers" , "strong animals" .)