Sue- you have put part of the clue in the title box and part in the question details box. I remember the clue from a few weeks ago but it would otherwise not mean much. The clue says SIGMA not stigma. they are consecutive letters of Greek alphabet
I did give a little hint earlier. Maybe the poster doesn't know how to reply to one's own questions- some don't seem to realise how to do it, and I think Sue has been away for a quite some time