Part of an equine pedigree (4)
I believe the answer is:
sire
'part of an equine pedigree' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for sire that I've seen before include "Bear" , "Old form of address to king - rise to it" , "Rise for male parent (4)." , "Stallion; beget" , "Ancestor" .)