Everton’s first opening game? (5)
I believe the answer is:
event
'game?' is the definition.
(game is a kind of event)
'everton's first opening' is the wordplay.
'everton's first' becomes 'e' (vst letter of 'everton').
'opening' becomes 'vent' (vent is a kind of opening).
'e'+'vent'='EVENT'
(Other definitions for event that I've seen before include "Function" , "ride competitively" , "Result; incident" , "Item in sports programme" , "Happening, incident" .)