Perhaps thief initially steals device for windscreen (6)

I believe the answer is:

swiper

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'perhaps thief initially steals' is the definition.
I don't know anything about this answer so I can't tell whether this works.

'device for windscreen' is the wordplay.
I cannot really understand how this works, but
'device' could be 'wiper' (wiper is a kind of device) and 'wiper' is located in the answer.
A single letter 's' remains which might be clued in a way I don't understand.
This explanation may well be incorrect...

Can you help me to learn more?

I've seen this clue in The Times.

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