Filmgoer sees this game between Mike and Oscar (4)
I believe the answer is:
golf
'filmgoer sees this game between mike and oscar' is the definition.
'golf' can be an answer for 'game' (I've seen this before). I'm not sure about the rest of the definition.
'filmgoer sees this game' is the wordplay.
I cannot quite see how this works, but
'game' could be 'go' (go is a kind of game) and 'go' is present in the answer.
This may be the basis of clue (or it may be nonsense).
(Other definitions for golf that I've seen before include "Foxtrot follower" , "Game involving woods and irons" , "The game some say spoils a good walk" , "Game on greens" , "Game played on links" .)