Boy absorbed by vacuous game in clearing (5)
I believe the answer is:
glade
'clearing' is the definition.
(I know that clearing can be written as glade)
'boy absorbed by vacuous game' is the wordplay.
'boy' becomes 'lad' (informal term for boy).
'absorbed by' indicates putting letters inside.
'vacuous' means to remove the middle letters.
'game' with its centre taken out is 'ge'.
'lad' placed within 'ge' is 'GLADE'.
'in' acts as a link.
(Other definitions for glade that I've seen before include "wood's open space" , "Woodland clearing" , "An open space in a forest" , "Forest clearing" , "Woodland opening" .)