Related Clues:

• Left to one's personal choice
• Too plain (anag.)
• Permissive one in platoon out of order
• Seen in a list perhaps, but it's not necessary
• Not required -- too plain, to put it horribly
• Voluntary one found in irregular platoon
• Unforced
• I plan too haphazardly but it's a matter of choice
• Work time on island left down to choice
• Unnecessary seats in line to be shifted
• At sea, a pilot? No, not required
• Do what you want with this pilot on a spin
• Voluntary work gets a lot in after training
• If you ask for it
• Saving face, Neil Innes sat out, surplus to requirements