Able to go to sleep and still not lose? (5)

I believe the answer is:

dormy

I'm a little stuck... Click here to teach me more about this clue!

'sleep and still not lose?' is the definition.
I know nothing about this answer so I can't tell whether this works.

'able to go' is the wordplay.
I cannot really understand how this works, but
'go' could be 'do' (doing is a kind of going) and 'do' is found in the answer.
This explanation may well be incorrect...

'to' acts as a link.

Can you help me to learn more?

I've seen this clue in the Evening Standard.

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