Best of Brussels? (4)

I believe the answer is:

tops

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

'best of brussels?' is the definition.
'tops' can be an answer for 'best' (I've seen this in another clue). I'm unsure of the 'of brussels?' bit.

'best of brussels?' is the wordplay.
'best' becomes 'top' (top can mean the very best).
'of brussels?' becomes 's' (I can't explain this - if you can you should give a lot more credence to this answer).
'top'+'s'='TOPS'

Can you help me to learn more?

(Other definitions for tops that I've seen before include "Goes beyond" , "The best" , "Beats" , "Betters" , "Surpasses; toys" .)

I've seen this clue in the Evening Standard.

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