Notes opening for arrival (6)
I believe the answer is:
advent
'for arrival' is the definition.
(advent is a kind of arrival)
'notes opening' is the wordplay.
'notes' becomes 'ad' (two musical notes).
'opening' becomes 'vent' (vent is a kind of opening).
'ad'+'vent'='ADVENT'
(Other definitions for advent that I've seen before include "when the Christmas shopping has to be done?" , "sort of calendar" , "The season leading up to Christmas" , "Church season" , "Pre-Christmas season for Christians" .)