A weapon returned, conservative, is of little value (8)

I believe the answer is:

nugatory

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'is of little value' is the definition.
I can't tell whether this defines the answer.

'a weapon returned conservative' is the wordplay.
'weapon' becomes 'gun' (gun is a kind of weapon).
'returned' shows that the letters should be reversed in order.
'conservative' becomes 'tory' (informal term for a Conservative Party member).
'a'+'gun'='agun'
'agun' backwards is 'nuga'.
'nuga'+'tory'='NUGATORY'

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(Other definitions for nugatory that I've seen before include "Worthless - trifling" , "Young art (anag) -- worthless" , "Any grout (anag) - trifling" , "Worthless or of no real value" , "Insignificant or trivial" .)

I've seen this clue in the Sydney Morning Herald.

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