Related Clues:

• Long, long sentence
• Word substituted FOR the last word of 23-Across
• Biographer's topic
• "That's __!"
• CEP word
• This puzzle's theme word
• Cabinet department with a windmill on its seal
• __ bar
• Solar product
• It can be conserved
• Board game whose earliest version came out in 1860
• Part of an Einsteinian equation
• The "it" in "He likes it! Hey Mikey!"
• Coal, gas or wind can supply it
• It may be green