Marmelise lock, stock and barrel a major player in Big Oil? (5)
I believe the answer is:
total
'oil?' is the definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Perhaps they are linked in a way I don't understand?
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for total that I've seen before include "Complete sum" , "French oil and gas company" , "wreck" , "Final tally" , "Comprising the whole" .)