Dirty cap removed and lubricated (5)
I believe the answer is:
oiled
'lubricated' is the definition.
('oil' can be a synonym of 'lubricate')
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for oiled that I've seen before include "greasy" , "Anointed" , "protected from rust?" , "wasted" , "Greased; drunk" .)