Spots fox up over Gravesend? (4)

I believe the answer is:

dots

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'spots' is the definition.
(I know this)

'fox up over gravesend?' is the wordplay.
'fox' becomes 'tod' (historic term).
'up' is a reversal indicator (in down clue: letters go upwards).
'over gravesend?' becomes 's' (I can't justify this - if you can you should give a lot more credence to this answer).
'tod' backwards is 'dot'.
'dot'+'s'='DOTS'

Can you help me to learn more?

(Other definitions for dots that I've seen before include "Tiny circles" , "Tiny circular shapes" , "Shorter signals in the Morse code" , "Very small round shapes" , "Short signals in Morse cods" .)

I've seen this clue in the Sydney Morning Herald.

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