What's coming from plug hole? (6)
I believe the answer is:
advent
'what's coming' is the definition.
(advent is the arrival or coming of something)
'plug hole?' is the wordplay.
'plug' becomes 'ad' (as in plugging a product).
'hole?' becomes 'vent' (vent is a kind of hole).
'ad'+'vent'='ADVENT'
'from' acts as a link.
(Other definitions for advent that I've seen before include "The coming of a religous period?" , "Period in church calendar" , "Season for a candle?" , "Arrival - time before Christmas" , "Pre-Christmas season for Christians" .)