Help UN agent desperate to get sizeable weapon (8,3)

I believe the answer is:

elephant gun

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'sizeable weapon' is the definition.
The definition suggests a singular noun which matches the answer.

'help un agent desperate' is the wordplay.
'desperate' indicates an anagram (a desperate or pathetic spelling).
'help'+'un'+'agent'='helpunagent'
'helpunagent' anagrammed gives 'ELEPHANT GUN'.

'to get' acts as a link.

Can you help me to learn more?

(Another definition for elephant gun that I've seen is " Large-calibre rifle".)

I've seen this clue in The Irish Times.

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