An athlete may take one in protest (4)
I believe the answer is:
knee
'an athlete may take one in protest' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for knee that I've seen before include "Leg hinge" , "Joint of the body" , "middle part of leg" , "Where the femur meets the tibia" , "Genuflector?" .)