A rotary tool used in burrowing (4)

I believe the answer is:

burr

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'a rotary tool' is the definition.
'burr' can be an answer for 'tool' (burr is a kind of tool). I'm unsure of the 'a rotary' bit.

I don't understand the rest of the clue.

Can you help me to learn more?

(Other definitions for burr that I've seen before include "Polish up slightly" , "The strong pronunciation of ''r''" , "Seed with sticky prickles" , "Soft regional accent" , "Whirring sound or plant seed-case that sticks" .)

I've seen this clue in the Evening Standard.

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