Related Clues:

• Thin blue line, say
• Ore deposit
• It goes to the heart
• Shrimp discard
• Way to one's heart
• Mother lode, e.g.
• Silver streak
• Inner tube?
• Blood's pathway
• Literary style
• Way to a man's heart?
• Part of an internal network
• Leaf feature
• Marble feature
• Special aptitude