Thank you all. Should have got apron, thought of prong straight away! Oh well, we learn every day. And off-stage so obvious. Was concentrating too hard on part of a house, not of house in the theatre sense!
danny / mac, I understand how the answer of apron was arrived at, but ethelburga has indicated the answer has 6 letters, but then shows known and unknown letters to be a 5 letter answer.