Crossword Genius

Given a drink, we tread unwarily (7)

Ross

I believe the answer is:

watered

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'given a drink' is the definition.
The answer and definition can be both related to change as well as being past participle verbs.
Perhaps they are linked in a way I don't understand?

'we tread unwarily' is the wordplay.
'we tread' anagrams to 'WATERED'.
Though, I'm not clear how the anagram is indicated.

Can you help me to learn more?

I've seen this clue in the Evening Standard.
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