Meeting to vex saint (5)
I believe the answer is:
tryst
'meeting' is the definition.
(I know that tryst is a type of appointment)
'vex saint' is the wordplay.
'vex' becomes 'try' (I've seen this in another clue).
'saint' becomes 'st' (abbreviation).
'try'+'st'='TRYST'
'to' is the link.
(Other definitions for tryst that I've seen before include "private meeting" , "Lump (of gold, etc)" , "Secret assignment" , "meeting-place" , "where lovers meet" .)