Left a politician with a disc and 1 litre of liquid petroleum (4,3)

'liquid petroleum' is the definition.
I know nothing about this answer so I can't tell whether this works.

'left a politician with a disc and 1 litre' is the wordplay.
I cannot quite understand how this works, but
'left' could be 'l' (common abbreviation) and 'l' is found within the answer.
'a' could be 'amp' (A is the symbol for the amp or ampere) and 'amp' is located in the answer.
'disc' could be 'o' (disc-shaped letter) and 'o' is present in the answer.
'1' could be 'i' (Roman numeral) and 'i' is present in the answer.
'litre' could be 'l' (abbreviation) and 'l' is present in the answer.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).

'of' is the link.

Can you help me to learn more?