Couple object in detail (4)
I believe the answer is:
item
This clue is a triple definition!
'couple' is the first definition.
(a romantic couple are 'an item')
'object' is the second definition.
(both can mean a thing)
'in' acts as a link.
'detail' is the third definition.
(I know that detail can be written as item)
(Other definitions for item that I've seen before include "Bit of information" , "Piece in paper" , "Single article on a list" , "story" , "Individual thing" .)