Couples found in bed, most regularly after sex (5)
I believe the answer is:
items
'couples' is the definition.
(a couple might be called an 'item')
'bed most regularly after sex' is the wordplay.
'regularly' indicates alternate letters (regularly take one letter, leave next etc.).
'after' says to put letters next to each other.
'sex' becomes 'it' (a common euphemism).
'bed'+'most'='bedmost'
The alternating letters of 'bedmost' are 'ems'.
'ems' after 'it' is 'ITEMS'.
'found in' is the link.
(Other definitions for items that I've seen before include "Articles or units on a list" , "Couples" , "partners" , "Times (anag.)" , "Things listed" .)