Requiring damned engine reconditioning (7)
I believe the answer is:
needing
'requiring' is the definition.
('need' can be a synonym of 'require')
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for needing that I've seen before include "Wanting" , "Requiring" , "Short of, lacking" , "Eden gin (anag.)" .)