Current keeping river hot and steamy (8)

I believe the answer is:

tropical

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'hot and steamy' is the definition.
(in the tropics)

I don't understand the rest of the clue.

(Other definitions for tropical that I've seen before include "extremely warm" , "Relating to hot and humid parts" , "Boiling" , "Fervidly hot" , "Hot and humid, near the equator" .)

I've seen this clue in The Telegraph.

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