Farm implement (10)
'farm implement' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for harrow that I've seen before include "Equipment provided for ground-breaking" , "Torment (at public school?)" , "and another [SCHOO]" , "Soil cultivator - English public school" , "It breaks up clods and covers seeds" .)