Crossword Genius

Stumbling on subsequent clue? (6,6)

Ross

I believe the answer is:

coming across

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

'stumbling' is the definition.
The definition and answer can be both related to thinking as well as being present participle verbs.
Maybe they are linked in a way I don't understand?

I don't understand the rest of the clue.

Can you help me to learn more?

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