Related Clues:

• Up on trends
• When doubled, start of a cheer
• 'I'm ___'
• When repeated, start of a cheer
• Sound repeated while marching
• Like jazz cats
• Like jazz musicians
• Like cool cats
• Up on the latest trends
• With it, '40s-style
• Knowledgeable
• Cool, in old slang
• Oft-replaced part
• In style
• Cool, to jazzmen