Related Clues:

• Ruth runs with heron
• Fret about wading bird seen by river
• Deplore being endlessly cruel
• Rue de Pierre Gretzky
• Sad to say, globetrotter fails to get blotto
• Beat oneself up over, say
• Sad to say, some overwater geraniums coming up
• Feeling for one who missed out
• Rue raising sample of winter geraniums
• Secondary proposition from man docked on lunar module
• "A man has cause for ___ only when he sows and no one reaps": Charles Goodyear
• 'We ___ to inform you . . .'
• Facepalm emotion
• In maths, a theorem proved to help to prove another one
• Step in a mathematical proof