Thin because squashed in a press? (6)

I believe the answer is:

sparse

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

'thin' is the definition.
(I know that thin can be written as sparse)

'because squashed in a press?' is the wordplay.
'a press' anagrams to 'SPARSE'.
Though, I'm not clear how this is indicated.

Can you help me to learn more?

(Other definitions for sparse that I've seen before include "Spares, being thin on the ground" , "not packed together" , "Thinly spread" , "Thinly populated" , "Thinly scattered, not dense" .)

I've seen this clue in the Evening Standard.

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