Is more cheerful when the dollar's risen? (5,2)

I believe the answer is:

bucks up

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'is more cheerful when' is the definition.
I can't tell whether this definition defines the answer.

'dollar's risen?' is the wordplay.
'dollar's' becomes 'bucks' (slang).
'risen?' becomes 'up' ('up' can be similar in meaning to 'risen').
'bucks'+'up'='BUCKS UP'

'the' acts as a link.

Can you help me to learn more?

(Other definitions for bucks up that I've seen before include "Hurries" , "becomes more cheerful" , "Encourages" .)

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

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