Sentimental, having conversely upset companion (5)

I believe the answer is:

crony

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'companion' is the definition.
(I've seen this before)

I cannot understand how the remainder of the clue works.

(Other definitions for crony that I've seen before include "China" , "Intimate companion" , "Close friend" , "mate" , "Sidekick" .)

I've seen this clue in The Times.

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