Badly built car needs a drop of engine oil (9)
I believe the answer is:
Here is my best explanation:
'oil' is the definition.
('lubricate' can be a synonym of 'oil')
'badly built car needs a drop of engine' is the subsidiary indication.
'badly' indicates an anagram.
'needs' means one lot of letters go next to another.
'a drop of' suggests taking the first letters.
The first letter of 'engine' is 'e'.
'builtcar' anagrammed gives 'lubricat'.
(Other definitions for lubricate that I've seen before include "Coat with oil to reduce friction", "Make slippery", "Apply oil/grease", "Oil (a mechanism)", "Oil, grease", "Grease, oil" and "Apply oil or grease to".)