Crossword Genius

Think constantly about source of water in river (5,2)

Ross

I believe the answer is:

dwell on

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'think constantly about' is the definition.
I can't judge whether this defines the answer.

'source of water in river' is the wordplay.
'source of water' becomes 'well' (water may come from a well).
'in' indicates putting letters inside.
'river' becomes 'Don' (Yorkshire river).
'well' put within 'don' is 'DWELL ON'.

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(Other definitions for dwell on that I've seen before include "Speak at length about" , "Linger over" , "Mull over" , "Ponder about" , "Think at length about" .)

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