Thoughts analysed as inherently repulsive (4)

I believe the answer is:

ugly

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'repulsive' is the definition.
(I've seen this in another clue)

I cannot understand how the rest of the clue works.

(Other definitions for ugly that I've seen before include "Sullen" , "Like an eyesore" , "Revolting" , "Menacing" , "Not pleasing to look at" .)

I've seen this clue in The Irish Times.

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