Singles-only holiday? (3-3,4)

I believe the answer is:

one-way trip

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'singles-only holiday?' is the definition.
I know nothing about this answer so I cannot judge whether this works.

'only holiday?' is the wordplay.
'only' becomes 'oneway' (I can't explain this - if you can you should believe this answer much more).
'holiday?' becomes 'trip' (I've seen this before).
'oneway'+'trip'='ONE-WAY TRIP'

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I've seen this clue in The Guardian.

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