Couple one encountered going west (4)
I believe the answer is:
item
'couple' is the definition.
(a romantic couple are 'an item')
'one encountered going west' is the wordplay.
'one' becomes 'i' (Roman numeral).
'encountered' becomes 'met' ('meet' can be a synonym of 'encounter').
'going west' shows that the letters should be reversed in order (letters heading to the west or left).
'met' written backwards gives 'tem'.
'i'+'tem'='ITEM'
(Other definitions for item that I've seen before include "Piece of news: unit" , "two with a link" , "One thing on a list" , "Single unit" , "point" .)