Dreadful ordeal in a border city (6)

I believe the answer is:

laredo

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

'city' is the definition.
(I know that Laredo is a city)

'dreadful ordeal in a border' is the wordplay.
'ordeal' anagrams to 'LAREDO'.
But, I am not sure how the anagram is indicated.

Can you help me to learn more?

(Other definitions for laredo that I've seen before include "Texan city" , "US-Mexico border town" , "US city" .)

I've seen this clue in The Sunday Times and The Times.

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