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This, and mortar, make a working combination (6)

Ross

I believe the answer is:

pestle

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

This clue might be a double definition.

'this and mortar' is the first definition.
The definition suggests a singular noun which matches the answer. I also know that 'mortar' relates to this answer.

'a working combination' is the second definition.
Although both the answer and definition are singular nouns, I can't understand how one could define the other.

'make' is the link.

Can you help me to learn more?

(Other definitions for pestle that I've seen before include "Tool for grinding in a mortar" , "found at pound shop?" , "A grinder or pounder" , "Small club for use with mortar" , "Small club for pounding substances in mortar" .)

I've seen this clue in the Evening Standard.
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