What might give an obtuse result? (10)

I believe the answer is:

protractor

'result?' is the definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.

I don't understand the remainder of the clue.

(Other definitions for protractor that I've seen before include "muscle" , "Geometry set item" , "Geometrical instrument" , "Angle-measuring device" , "draughtsman may use this" .)

I've seen this clue in The Times.

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