Australasian acquires land mass (4)

I believe the answer is:

asia

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

'land mass' is the definition.
(I've seen this before)

'australasian acquires' is the wordplay.
'ASIA' is hidden within the letters.
But, I am unsure how this is indicated.

Can you help me to learn more?

(Other definitions for asia that I've seen before include "Populous continent" , "Continental land mass" , "Heavily populated area" , "Populous area" , "A is A (anag)" .)

I've seen this clue in The Mirror.

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