Number 500 looks agreeable (3)

I believe the answer is:

nod

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'looks agreeable' is the definition.
I can't judge whether this defines the answer.

'number 500' is the wordplay.
'number' becomes 'no' (abbreviation).
'500' becomes 'D' (Roman numeral for 500).
'no'+'d'='NOD'

Can you help me to learn more?

(Other definitions for nod that I've seen before include "OK" , "Gesture; agree" , "Assenting head gesture" , "It's said to be as good as a wink" , "Indicate 25 [YES]" .)

I've seen this clue in the Evening Standard.

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