Thanks for posting more of the cert, although it should help loads it's still a struggle! The first letter looks most like the 'A' of Ann in the witness's name but with the bottom of the letter not showing, the next letter could be a 'g' and I thought it might be Agric. Builder but probably not. Candleflame's Organ Builder is a possibility but I wondered if it might be something to do with ship building as there are two shipowners on the cert? Maybe someone local to Durham would know a dialect word/name for a type of ship that it could be?
This is really tantalising, we should be able to read it but it's still a puzzle.
Heather