Crossword Genius

A gust swirling, going through Lisbon (5)

Ross

I believe the answer is:

tagus

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'going through lisbon' is the definition.
Although both the answer and definition are singular nouns, I can't see how one could define the other.

'a gust swirling' is the wordplay.
'swirling' indicates anagramming the letters (letters get swirled around).
'a'+'gust'='agust'
'agust' is an anagram of 'TAGUS'.

Can you help me to learn more?

(Other definitions for tagus that I've seen before include "Portuguese river flowing to sea near Lisbon" , "Longest river of Iberian peninsular" , "Current" , "Longest river of Iberian peninsula" , "banker" .)

I've seen this clue in The Globe and Mail.
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