Train tickets found when darkness lifts? (3,7)

I believe the answer is:

day returns

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'train tickets' is the definition.
'day returns' can be an answer for 'tickets' (day return is a kind of ticket). I am not sure about the 'train' bit.

I don't understand how the rest of the clue works.

Can you help me to learn more?

I've seen this clue in The Guardian.

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