On return determined to hold pub game (6)
I believe the answer is:
tennis
'game' is the definition.
(tennis is a kind of game)
'on return determined to hold pub' is the wordplay.
'on return' says the letters should be written backwards.
'determined' becomes 'set' (synonyms).
'to hold' means one lot of letters goes inside another.
'pub' becomes 'inn' (an inn is a type of pub).
'set' placed around 'inn' is 'sinnet'.
'sinnet' reversed gives 'TENNIS'.
(Other definitions for tennis that I've seen before include "Sport on a court" , "Table -, - elbow" , "court contest" , "Medieval, originally French, sport, codified by the British" , "Pete Sampras's sport" .)