Crossword Genius

One strongly instrumental in building a tower amid water? (5,4)

Ross

I believe the answer is:

power tool

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

'one strongly instrumental in' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how they can define each other.

'building a tower amid water?' is the wordplay.
'building' indicates an anagram.
'amid' is an insertion indicator.
'water?' becomes 'pool' (pool is a kind of water).
'tower' is an anagram of 'werto'.
'werto' put into 'pool' is 'POWER TOOL'.

Can you help me to learn more?

(Another definition for power tool that I've seen is " drill, perhaps".)

I've seen this clue in the Evening Standard.
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