Ancient land, extremely dry? (14)

I believe the answer is:

supercontinent

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'ancient' is the definition.
I know nothing about this answer so I can't judge whether this works.

'land extremely dry?' is the wordplay.
'land extremely' becomes 'super' (I am not sure about this - if you are sure you should believe this answer much more).
'dry?' becomes 'continent' (I've seen this before).
'super'+'continent'='SUPERCONTINENT'

Can you help me to learn more?

(Another definition for supercontinent that I've seen is " Large early landmass".)

I've seen this clue in The Sunday Times.

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