Singletons? (6,6)

I think it could be either:

Which length description are you looking for?:

6,6

lonely hearts

'singletons?' is the definition.
(I've seen this before)

This is all the clue.

(Other definitions for lonely hearts that I've seen before include "Unhappily unattached persons?" , "They need dates" , "singletons?" , "Singles" , "column in paper" .)

I've seen this clue in The Guardian.

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