As part of a big update to its car, McLaren introduced a new front wing at Singapore. The new wing has a totally revised stacked element, in fact the one element featured at Spa and Monza is now replaced by two seperate elements. The outer one is a simple, small two-element wing attached to the main front wing endplate. The wing itself has its own endplate as well, as indicated by an arrow.
The more inward part of the stacked element looks rather more sophisticated and connects to the wing's base panel which is now even more curved. Contrary to previous McLaren front wings, the stacked element is now also decoupled from the front wing adjuster, the most inward vertical panel on the wing.
Also note that McLaren did not fit the rest of their update package to the car this weekend for reliability reasons. It will be introduced at the next race.