Patella site (4)
I believe the answer is:
knee
'patella site' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for knee that I've seen before include "Capped joint?" , "proposal might be made on one" , "may present problem to maid" , "Where the femur meets the tibia" , "Technical name for this joint is genu" .)