Related Clues:

• The heart of the matter
• Heart and soul
• Jet competitor
• Feature of this crossword
• Composer's base
• Motif
• Subject matter
• Compass direction
• Signature tune
• English assignment
• Crossword topic
• Basic idea
• School paper
• Be rude, in a way
• First word follower of 17, 64-Across and 11, 29-Down