Salt dosage in need of amendment (3,3)

I believe the answer is:

sea dog

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'salt' is the definition.
(synonyms)

'dosage in need of amendment' is the wordplay.
'dosage' anagrams to 'SEA DOG'.
However, I am not sure how the anagram is indicated.

Can you help me to learn more?

(Other definitions for sea dog that I've seen before include "Experienced mariner" , "Old tar" , "'Old salt (3,3)'" , "Ancient Mariner" , "Experienced sailor (colloq.)" .)

I've seen this clue in The Times.

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