Twin to obstruct red-head Australian model openly determined to make shotgun (6-9)

I believe the answer is:

double-barrelled

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'model openly determined to make shotgun' is the definition.
I can't tell whether this definition defines the answer.

'twin to obstruct red-head australian' is the wordplay.
'twin' becomes 'double' (identical twins are each other's doubles).
'to obstruct' becomes 'bar' (barring is a kind of obstructing).
'red-head' becomes 'r' (head letter of 'red-').
'australian' becomes 'elled' (I can't justify this - if you can you should believe this answer much more).
'double'+'bar'+'r'+'elled'='DOUBLE-BARRELLED'

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

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