I encountered returning couple (4)
I believe the answer is:
item
'couple' is the definition.
(a romantic couple are 'an item')
'i encountered returning' is the wordplay.
'encountered' becomes 'met' ('meet' can be a synonym of 'encounter').
'returning' is a reversal indicator.
'met' in reverse letter order is 'tem'.
'i'+'tem'='ITEM'
(Other definitions for item that I've seen before include "Two in a romantic relationship?" , "Article (on list or in news)" , "'One thing, poor mite (4)'" , "One thing on a list" , "pair?" .)