Sire (6)
(Other definitions for beget that I've seen before include "Give rise to; create (children)" , "Engender" , "Bring about, cause" , "Produce (child) (archaic)" , "Sire" .)
'sire' is the definition.
(synonyms)
This is all the clue.
(Other definitions for father that I've seen before include "and 13: Jolly gift-deliverer" , "dad" , "So-called priest" , "Progenitor" , "Sire" .)