Related Clues:

• One of two or possibly three going about one
• One or other
• One of two or three damaged I let through
• One of two or three compiled I go through
• One of two, or one in three perhaps
• Medium supposedly taking one in as a first option?
• It introduces alternatives, i.e. number over one
• Her tie (anag.)
• Hesitate with opening key change -- the one or the other?
• 'Your choice'
• One of two that is returned to the right
• No matter which (of two)
• One of the two
• Two-options-only
• One of two I plunged into volatile liquid