Should misguided Republican refuse to use pun of this quality? (7)

I believe the answer is:

calibre

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'this quality?' is the definition.
(synonyms)

I cannot understand how the remainder of the clue works.

(Other definitions for calibre that I've seen before include "Level of ability; bore" , "Diameter of bore of firearm" , "Ability; barrel diameter" , "bore on the Tube?" , "weapon's bore?" .)

I've seen this clue in The Irish Times.

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