Squander brief daytime kip, getting maximally flushed? (9)

I believe the answer is:

blowsiest

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

'brief daytime kip getting maximally flushed?' is the definition.
I can't judge whether this definition defines the answer.

'squander' is the wordplay.
I cannot quite understand how this works, but
'squander' could be 'blow' (synonyms) and 'blow' is located in the answer.
This may be the basis of the clue (or it may be nonsense).

Can you help me to learn more?

I've seen this clue in The Independent.

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