Making adjustments to a garment that's revealing (7,3)

I believe the answer is:

letting out

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

'revealing' is the definition.
('let out' can be a synonym of 'reveal')

'making adjustments to a garment' is the wordplay.
I cannot really see how this works, but
'making' could be 'letting' (letting is a kind of making) and 'letting' is found within the answer.
The remaining letters 'out' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...

'that's' is the link.

Can you help me to learn more?

I've seen this clue in the Evening Standard.

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