Jar filled with a colourful liquid (5)

I believe the answer is:

paint

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'jar' is the definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Perhaps they are linked in a way I don't understand?

I cannot understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for paint that I've seen before include "Item used by 23 Across" , "Catch a likeness" , "Eg, emulsion or gloss" , "Decorative coating" , "Coloured coating" .)

I've seen this clue in The Times.

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