Coming (6)
'coming' is the definition.
(advent is the arrival or coming of something)
This is all the clue.
(Other definitions for advent that I've seen before include "observed by Christian church" , "Arrival - time before Christmas" , "Arrival (with calendar?)" , "appearance" , "Pre-Christmas season for Christians" .)
(Other definitions for future that I've seen before include "Time that is 4 down" , "Time still to come" , "Beyond the present" , "Hereafter" , "What is yet to pass" .)
'coming' is the definition.
(I know that coming can be written as arrival)
This is all the clue.
(Other definitions for arrival that I've seen before include "Achievement of destination" , "Act of coming" , "Appearance (at a destination)" , "Advent" , "Coming - comer" .)