Game theory won't be marked (10)
I believe the answer is:
noteworthy
'be marked' is the definition.
(thesaurus)
'game theory won't' is the wordplay.
'game' indicates an anagram (solving anagrams is a game).
'theory'+'wont'='theorywont'
'theorywont' anagrammed gives 'NOTEWORTHY'.
(Other definitions for noteworthy that I've seen before include "Signal" , "Interesting, significant" , "important" , "Of significance" .)