Knee protectors (4)
I believe the answer is:
pads
'knee protectors' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for pads that I've seen before include "Protective guards worn by sportspeople" , "Lines or stuffs with soft material" , "tablets" , "Lines, or stuffs with soft materials" , "flats?" .)