Fizzes fresh sea-water, tungsten-free (7)

I believe the answer is:

aerates

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'fizzes' is the definition.
The definition and answer can be both related to change as well as being verbs in their -s form.
Perhaps they are linked in a way I don't understand?

I can't explain the rest of the clue.

Can you help me to learn more?

(Other definitions for aerates that I've seen before include "Pumps carbon dioxide into" , "Brings gas" , "uses fork to do it?" , "Puts fizz into a drink" , "Adds carbon dioxide to liquid under pressure" .)

I've seen this clue in the Sydney Morning Herald.

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