The kneecap (7)
I believe the answer is:
patella
'the kneecap' is the definition.
('patella' can be a synonym of 'kneecap')
This is the entire clue.
(Other definitions for patella that I've seen before include "showing a bit of leg" , "Joint cover" , "Kneecap (anatomy)" , "positioned on each knee" , "A pallet (anag.)" .)