Temporary accommodation's insulation is disappointing (4,4)

I believe the answer is:

lets down

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

'insulation is disappointing' is the definition.
I can't judge whether this defines the answer.

'temporary accommodation's' is the wordplay.
I cannot quite see how this works, but
'accommodation's' could be 'lets' (I've seen this in other clues) and 'lets' is found within the answer.
The remaining letters 'down' is a valid word which might be clued in a way I don't understand.
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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