Fresh guarantee for the American dollar (9)

I believe the answer is:

greenback

I'm a little stuck... Click here to teach me more about this clue!

'american dollar' is the definition.
'greenback' can be an answer for 'dollar' (I've seen this before). I'm not certain of the 'american' bit.

'fresh guarantee for' is the wordplay.
'fresh' becomes 'green' (I've seen this before).
'guarantee for' becomes 'back' (I can't justify this - if you can you should give a lot more credence to this answer).
'green'+'back'='GREENBACK'

'the' acts as a link.

Can you help me to learn more?

(Other definitions for greenback that I've seen before include "money" , "Dollar bill" .)

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

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