Number 500 looks agreeable (3)

I believe the answer is:

nod

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

'number 500' is the wordplay.
'number' becomes 'no' (abbreviation for 'number'**).
'500' becomes 'd' ('d' can be a synonym of '500').
'no'+'d'='NOD'

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(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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