This may light up the game (5)
I believe the answer is:
match
'game' is the definition.
(eg a football match)
'this may light up the' is the wordplay.
I cannot quite see how this works, but
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is present in the answer.
The remaining letters 'mach' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for match that I've seen before include "Game - pairing - lucifer" , "Tally; game" , "Stick in a box?" , "Suit; fixture" , "Lighter; contest" .)