Dele Alli was once a young talented player with a very promising future with the likes of Lingard, he performed brilliantly well for his former club, his movement to Besiktas is a welcome development, I believe he will be a regular player in his new club maybe he might pick up form and return to his very best and promptly return to EPL in no too distant future, it's unfortunate that Everton has to.release him with no contribution to the team in last season and this season, I think he still has a lot to offer in his new club
Dele Alli is a talented player whom I personally admired when he was playing with Tottenham, great skill, good pace and very comfortable in attack and scoring goals, too bad he went down the pecking order and was almost forgotten for his good days. Moving to Besiktas should be a good move for him, he would get better playing time, fresh atmosphere and another opportunity to find his form and improve his game again. Best of luck to him.