Earlier, pair drinking port (5)
I believe the answer is:
prior
'earlier' is the definition.
('prior' can be a synonym of 'earlier')
'pair drinking port' is the wordplay.
'pair' becomes 'pr'.
'drinking' means one lot of letters goes inside another.
'port' becomes 'rio' (I've seen this before**).
'pr' going around 'rio' is 'PRIOR'.
(Other definitions for prior that I've seen before include "writer of epigrammatic verse" , "English keeper" , "Already arranged" , "head of a house of friars" , "Former - chief of religious house" .)