Possible Clues:

• Sandwich alternative
• 'A,' in pilot shorthand
• "A," in pilot shorthand
• First letter of the NATO phonetic alphabet
• __ Romeo (import from 17 Down)
• Letter opposite Zulu
• Lead-in for Romeo
• A as in amateur radio
• Letter before Lima and after Foxtrot when spelling 27-Down
• First letter in the NATO phonetic alphabet