An easy one to paint? (6)

I believe the answer is:

sitter

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'an easy one' is the definition.
(eg an easy shot in football)

I cannot understand how the rest of the clue works.

(Other definitions for sitter that I've seen before include "easy target" , "Person posing for a portrait" , "Child-minder of sedentary disposition" , "Child minder, sounds sedentary" , "Artist's model - an easy catch" .)

I've seen this clue in the Evening Standard.

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