Possible Clues:

• Misfit
• Margaret, being old-fashioned, is a misfit
• Apt username for Margaret, the geometry teacher?
• Succeeded as salesman, say, who's in the wrong job?
• Misfit in group of sportsmen almost acquiring agent for example
• *Nonconformist, idiomatically
• Something that's hardly fitting?
• Potential misfit
• Margaret is so old-fashioned she won't fit in with 1 across
• Never fit to go into 6 down