Crippling one motorway, I tell the police, is about oil giant (12)

'police is about oil giant' is the definition.
I can't judge whether this defines the answer.

'crippling one motorway i tell' is the wordplay.
I cannot quite see how this works, but
'one' could be 'i' (Roman numeral) and 'i' is present in the answer.
'motorway' could be 'm' (as in motorway names - M1, M4 etc) and 'm' is found within the answer.
'i' is within the answer.
'tell' could be 'sing' (I've seen this in other clues) and 'sing' is present in the answer.
This may be the basis of the clue (or it may be nonsense).

'the' acts as a link.

Can you help me to learn more?