Former partner sent Rick to speak to the oddball (9)

I believe the answer is:

eccentric

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'the oddball' is the definition.
(synonyms)

I cannot understand how the remainder of the clue works.

(Other definitions for eccentric that I've seen before include "card" , "Crank" , "Odd, unusual" , "Given to odd behaviour" , "Unconventionally strange" .)

I've seen this clue in the Sydney Morning Herald.

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