Possible Clues:

• Movement attracting support
• Reportedly prohibited joker having as topic fashionable movement
• Cause whose support is growing
• Stop fellow about to shake crowded vehicle?
• One's got on in an endeavour to go with the flow
• Movement attracting lots of followers
• Popular movement
• *Popular cause to jump on
• Some will want to jump on this fashionable type of tour bus
• Gang with silver on vehicle