Related Clues:

• As a result
• Hence
• Error indicator
• Order to attack, with 'on'
• Set a setter (on)
• Canine command
• Urge to attack, with 'on'
• '___ 'em, Rover!'
• [their mistake, not mine]
• Quotation notation
• See 21-Across
• Accordingly
• Quotation addition
• 'Tantum ___' (part of a Eucharist hymn)
• Proof part