Related Clues:

• First-sight phenomenon
• Deep space, for the most part
• Type of code
• It's nothing, really
• It means nothing to 45-Across
• None whatever
• All-conquering thing
• Cancel out
• Not even one
• Horrible grade on a test
• Puppy follower?
• Kind of tolerance
• -
• Nadir
• Unimpressive score