4: Go out of bounds, perhaps
 5: One who knows the score
 7: Having only one component
 21: Van Gogh's love offering
 23: Using both sides with equal frequency (like the letters in this puzzle's answer grid?)
 38: Outdated communication service
 44: Helios, to the Romans
 46: Some wind instruments
 52: Modern form of communication
 58: Word before irons or chains