A contest to be equal to (5)
I believe the answer is:
match
I believe this is a double definition.
'a contest' is the first definition.
(match is a kind of contest)
'be equal to' is the second definition.
(I've seen this in another clue)
'to' acts as a link.
(Other definitions for match that I've seen before include "Contest; correspond" , "Partnership" , "Light" , "Equivalent" , "Go together" .)