Prone to being long-winded? (9,3)

I believe the answer is:

stretched out

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This could be a double definition.

'prone' is the first definition.
Although both the answer and definition are adjectives, I cannot see how they can define each other.

'long-winded?' is the second definition.
(thesaurus)

'to being' acts as a link.

Can you help me to learn more?

I've seen this clue in The Globe and Mail.

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