Two women - one is excessively optimistic (9)

I believe the answer is:

pollyanna

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'excessively optimistic' is the definition.
I can't judge whether this defines the answer.

'two women one' is the wordplay.
'two women' can mean two substitutions for 'woman'.
'woman' becomes 'polly' (**).
'woman' becomes 'ann'.
'one' becomes 'a'.
'polly'+'ann'+'a'='POLLYANNA'

'is' is the link.

Can you help me to learn more?

(Other definitions for pollyanna that I've seen before include "Incurable optimist" , "eternal optimist" , "Naively optimistic type" , "Over-cheerful person" , "Over-optimistic person" .)

I've seen this clue in the Irish Times.

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