Complaint of the motorist using too much petrol? (11)
I believe the answer is:
consumption
This clue might be a double definition.
'complaint of the motorist' is the first definition.
'consumption' can be an answer for 'complaint' (consumption is a kind of health problem). I am unsure of the 'of the motorist' bit.
'using too much petrol?' is the second definition.
'consumption' can be an answer for 'using' (thesaurus). I am unsure of the 'too much petrol?' bit.
Can you help me to learn more?
(Other definitions for consumption that I've seen before include "Tuberculosis" , "See 7" , "that may be conspicuous" , "disorder" , "Eating" .)