What the golfer went round in, when under the weather? (5,3)

I believe the answer is:

below par

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'under the weather?' is the definition.
(thesaurus)

I cannot understand how the remainder of the clue works.

(Other definitions for below par that I've seen before include "Lower than the average, as in golf score ( 5, 3)" , "Not in full health" , "Out of sorts" , "Not up to usual standard, like golfer" , "Worse than usual" .)

I've seen this clue in the Evening Standard.

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