After thinking for hours I can only come up with a pretty crazy idea:COATRACK,which is a kind of tree (!),and consists of CO (company=firm) AT RACK (in the d's chair=being tortured)!Even then I can't quite explain "pull",unless pull in = stop.May be rubbish! You realize---as I didn't before googling---that the dentist's chair = binge drinking,but couldn't find any trees whose beginning + ending would form binge or any such synonym.The lists of trees in Collins Million Word Crossword Dictionary & Bradfords are pretty long but unproductive. I've no doubt the answer is much simpler, but I did try!!!