Conundrum to resolve in game (6)
I believe the answer is:
enigma
'conundrum' is the definition.
(synonyms)
'resolve in game' is the wordplay.
'resolve' indicates an anagram (I've seen 'resolved' mean this).
'in'+'game'='ingame'
'ingame' anagrammed gives 'ENIGMA'.
'to' is the link.
(Other definitions for enigma that I've seen before include "Difficult problem" , "closed book" , "Puzzle for gaming" , "Mysterious or puzzling thing" , "WWII cipher" .)