Large moulding giving audible sign (5)

I believe the answer is:

torus

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'large moulding' is the definition.
'torus' can be an answer for 'moulding' (I've seen this before). I'm not certain of the 'large' bit.

I don't understand the remainder of the clue.

Can you help me to learn more?

(Other definitions for torus that I've seen before include "Architectural moulding" , "Ring shape" , "Ring-doughnut shape" , "Shape of doughnut" , "Doughnut-shaped solid" .)

I've seen this clue in The Daily Express.

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