Patella's place (4)
I believe the answer is:
knee
'patella's place' 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 "One has a cap" , "Hinged joint" , "This is capped by the patella" , "It jerks reactively" , "Major joint in leg" .)