Crossword Genius

On the same side starting for all sides today (4)

Ross

I believe the answer is:

with

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'on' is the definition.
Both the answer and definition are adverbs. Perhaps there's a link between them I don't understand?

I can't explain the remainder of the clue.

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(Other definitions for with that I've seen before include "See 5" , "In the presence of" , "Characterised by" , "By means of" , "In spite of" .)

I've seen this clue in The Irish Times.
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