Crossword Genius

Bottomless River Plate's source (4)

Ross

I believe the answer is:

deep

'bottomless' is the definition.
(similar in meaning)

'river plate's source' is the wordplay.
'river' becomes 'dee' (River Dee).
'source' says to take the initial letters (source can mean a beginning or origin).
The first letter of 'plates' is 'p'.
'dee'+'p'='DEEP'

(Other definitions for deep that I've seen before include "Sunk low" , "Mysterious" , "Bottomless" , "profoundly" , "Extending far down" .)

I've seen this clue in The Telegraph and The Sun.
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