Spilling of gore at sacrifice (6)
I believe the answer is:
'sacrifice' is the definition.
(to forego something is to give it up)
'spilling of gore' is the wordplay.
'spilling' indicates anagramming the letters.
'ofgore' with letters rearranged gives 'FOREGO'.
'at' acts as a link.
(Other definitions for forego that I've seen before include "Go without or precede" , "Go without, give up" , "Go without (something desirable)" , "Surrender" , "Manage without" .)