Cliff oddly lacking energy before game (4)
I believe the answer is:
golf
'game' is the definition.
(golf game is a kind of game)
'cliff oddly lacking energy before' is the wordplay.
'oddly lacking' indicates alternate letters.
'energy' becomes 'go' (I've seen this in other clues**).
'before' is a charade indicator (letters next to each other).
The alternate letters of 'cliff' are 'lf'.
'lf' put after 'go' is 'GOLF'.
(Other definitions for golf that I've seen before include "Irons and woods sport" , "Game; G (radio comms.)" , "Leonhard -, Swiss mathematician/physicist" , "Code word for the letter G" , "Ball game" .)