At intervals, Haitian roughly demarcates arid expanse (7,6)

I believe the answer is:

atacama desert

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'arid expanse' is the definition.
Although both the answer and definition are singular nouns, I can't understand how one could define the other.

'at intervals haitian roughly demarcates' is the wordplay.
'at intervals' indicates alternate letters (letters are taken at regular intervals).
'roughly' indicates anagramming the letters.
The alternate letters of 'haitian' are 'ata'.
'demarcates' is an anagram of 'camadesert'.
'ata'+'camadesert'='ATACAMA DESERT'

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(Other definitions for atacama desert that I've seen before include "barren landscape" , "S. American wilderness" , "Desolate area of Chile" , "Barren region of Chile" , "Arid region in Chile" .)

I've seen this clue in The Times.

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