The Clippers have been linked to Anderson for a while, all the way back to late June. They are still weak on the wings, with Wes Johnson and Luc Mbah a Moute being the only natural small forwards on the roster. Alan will slide into 3rd on the depth chart, but I would assume he gets minutes at some point this year, especially if the Clippers go small.
Anderson will turn 34 in October, and this will be his 8th season in the NBA (he played in Europe for several years). Alan is a "3 and D" wing who shoots 34.5% for his career from downtown, but he can take them in volume, and has never played with a point guard the caliber of Chris Paul. Hopefully he will be able to hit closer to 40% this year if called upon to play in the rotation. Anderson is 6'6, 200 pounds, and is able to defend both the 2 and the 3 at a respectable level.
Anderson played only 13 games for the Washington Wizards last year, as he underwent several surgeries on his ankles. He is supposedly well on the way to recovery, and should be ready to go for the start of the season. Alan is a great locker room guy who John Wall reportedly wanted back in DC. As long as he helps out on the bench and fills in competently when needed, he will be a good get on the minimum.
This does mean the Clippers roster now stands at a full 15, which means the offseason is effectively over for them. The players on the team now will be the squad entering the season, barring a significant trade of some kind (unlikely at this point), or any potential fallout from Paul Pierce retiring.