No space in police state for the gents (6)

I believe the answer is:

toilet

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

'no' is the definition.
Although both the answer and definition are singular nouns, I can't understand how one could define the other.

I can't explain the rest of the clue.

Can you help me to learn more?

(Other definitions for toilet that I've seen before include "It means washing" , "WC" , "Lavatory paper" , "something to go on?" , "Smallest room" .)

I've seen this clue in the Irish Times (Crosaire) and the Irish Times.

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