Steady weather set to turn stormy (10)

I believe the answer is:

sweetheart

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'steady' is the definition.
(synonyms)

'weather set to turn stormy' is the wordplay.
'weather set' anagrams to 'SWEETHEART'.
But, I'm unsure how this is indicated.

Can you help me to learn more?

(Other definitions for sweetheart that I've seen before include "Boy- or girlfriend" , "Term of endearment" , "Darling" , "Darlin'"" , "ducks" .)

I've seen this clue in The Telegraph.

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