Get in bed, beginning to enjoy game (8)
I believe the answer is:
cribbage
'game' is the definition.
(cribbage is a card game)
'get in bed beginning to enjoy' is the wordplay.
'get' becomes 'bag' (bag can mean to secure or obtain).
'in' means one lot of letters goes inside another.
'bed' becomes 'crib' (bed for a child).
'beginning to' says to take the initial letters.
The first letter of 'enjoy' is 'e'.
'crib'+'e'='cribe'
'bag' inserted inside 'cribe' is 'CRIBBAGE'.
(Other definitions for cribbage that I've seen before include "Card-game" , "activity for couple sitting at table" , "Card game for two to four players" , "SPORT/GAME" , "Card game with a winning score of 121" .)