Tower made of alloy, last bit secured by drill (7)

I believe the answer is:

steeple

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'tower' is the definition.
(I know that steeple is a type of tower)

I can't explain the remainder of the clue.

(Other definitions for steeple that I've seen before include "Pet eels (anag)" , "Tall tower with spire on top of church" , "Pointed structure" , "point" , "Tall building" .)

I've seen this clue in The Times.

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