One look by police at troublemaker provides possible reason for crash (5,5)

'police at troublemaker provides possible reason for crash' is the definition.
I don't know anything about this answer so I can't tell whether it can be defined by this definition.

'one look' is the wordplay.
I cannot quite understand how this works, but
'one' could be 'i' (Roman numeral) and 'i' is found in the answer.
'look' could be 'lo' (archaic exclamation meaning 'look!') and 'lo' is found within the answer.
This may be the basis of the clue (or it may be nonsense).

'by' is the link.

Can you help me to learn more?