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Thing
that
makes
loving
couple
…
(4)
Thing that makes loving couple … (4)
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The whole clue is the definition (& lit or double definition).
How the clue works
The definition is Thing — as in any old object or article — and loving couple does the same job from the other end, since two people in a romance are said to be an item. It's a double definition, both halves pointing straight at the same word.