Excellent answer Calibax but poster should really help more by posting with full information, he appears to always post in this manner despite numerous requests.
Andy - you can join in on your own threads by replying to your own question to add any missing info. It's better to give the full clue, letter count and perhaps known pattern. Don't press Ask button until you have given all the details. It's been suggested before but maybe you didn't return so haven't seen it.