Doom to terrible feat (4)
I believe the answer is:
fate
'doom' is the definition.
(I've seen this before)
'terrible feat' is the wordplay.
'terrible' indicates an anagram.
'feat' is an anagram of 'FATE'.
'to' is the link.
(Other definitions for fate that I've seen before include "Inevitable destiny" , "Predetermined end" , "What must be" , "Lot -- doom" , "One's lot" .)