Crossword Genius

What’s in water regularly dissolves (4)

Ross

I believe the answer is:

isle

I'm a little stuck... Click here to teach me more about this clue!

'what's in water' is the definition.
I can't judge whether this defines the answer.

'regularly dissolves' is the wordplay.
'regularly' indicates alternate letters (regularly take one letter, leave next etc.).
The alternate letters of 'dissolves' are 'ISLE'.

Can you help me to learn more?

(Other definitions for isle that I've seen before include "The Lake ... of Innisfree (W.B.Yeats)" , "Lilliput, say" , "Small bit of land surrounded by water" , "Eg, Sheppey" , "This could be key" .)

I've seen this clue in The Times.
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