Possible Clues:

• Transport chief hoping for donations from the passengers?
• Transport chief playing for money
• Entertaining transport supremo?
• Cheat, in error, playing for cash
• Transport leader playing on the Underground, perhaps?
• Transport chief performing in the street?
• Performing in the street for money
• British leader's useless in providing amusement
• Go downhill, dividing illicit payment for performing illicitly
• 'Elvis' sits by vehicle making music for those passing by