Winning answer had to involve ultimate in knowledge (5)
I believe the answer is:
ahead
'winning' is the definition.
(I've seen this before)
'answer had to involve ultimate in knowledge' is the wordplay.
'answer' becomes 'a' (abbreviation eg in Q and A).
'to involve' is an insertion indicator.
'ultimate in' indicates one should take the final letters.
The last letter of 'knowledge' is 'e'.
'had' going around 'e' is 'head'.
'a'+'head'='AHEAD'
(Other definitions for ahead that I've seen before include "In front as in race" , "In the vanguard" , "In the future" , "Forwards" , "In the lead, in advance" .)