Extended cat gets big gun (4,3)

I believe the answer is:

long tom

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'big gun' is the definition.
'Long Tom' can be an answer for 'gun' (thesaurus). I'm unsure of the 'big' bit.

'extended cat' is the wordplay.
'extended' becomes 'long-' (similar in meaning).
'cat' becomes 'tom' (a tom is a male cat).
'long'+'tom'='LONG TOM'

'gets' is the link.

Can you help me to learn more?

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

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