I have "A Sea of Words", a lexicon to Patrick O'Brian's books. I have looked up every synonym of hewing I can think of, without success. If the answer is clipper, it's a very poor clue, since "hewer" means using an axe.
I bought my son a splitting axe for Christmas, causing great hilarity at Tool Station. "You mayn't be all that fond of your husband, but there's no need to go that far".Such great wit.