Crossword Genius

Pure milk when endlessly churned becomes more clotted (7)

Ross

I believe the answer is:

lumpier

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'more clotted' is the definition.
Both the answer and definition are comparative adjectives. Maybe they are linked in a way I don't understand?

I cannot understand how the rest of the clue works.

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(Other definitions for lumpier that I've seen before include "more uneven" , "Having more bulges" , "With more large bits" .)

I've seen this clue in The Independent.
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