Arkansas Governor Bill Clinton is looking more and more like a candidate for the Democratic Presidential nomination. BUSINESS WEEK has learned that the five-term governor has wrapped up Robert A. Farmer, treasurer of the Democratic National Committee and chief moneyman for the 1988 Dukakis campaign, as his top fund-raiser. Farmer won't comment. Beyond that coup, Clinton surrogates in the Democratic Leadership Council, a group of moderates, have begun seeking advice from party pros about a campaign manager. Meanwhile, Senator Lloyd Bentsen (D-Tex.), the party's 1988 vice-presidential nominee, has indicated that he would be willing to head the ticket in `92 if Democrats need a unifying candidate.