The steamy video sees the 34-year-old singer roll around and dance provocatively on a bed before getting close to the 33-year-old rapper. The former couple filmed the video in October following their September split.
Milian and Lil Wayne were together a year, and initially said they broke up because the timing wasn't right. The pair remained friends after their split, but the singer appeared to slam Lil Wayne for spending time with his ex-partner, Dhea Sodano, on Thanksgiving.
"Stop telling me you love me. Stop asking me to come see you. I am most definitely not interested. #BeenOverIt #HappyNoThanksgiving #Single," she tweeted, then later deleted.
Milian told The Meredith Vieira Show she still loves Lil Wayne in October, but claimed she and the rapper broke up because he cheated on Christina Milian Turned Up the next month. The singer said at the time, "I've never loved anyone the way that I love Wayne."
"Do It" is the third single to debut from Milian's forthcoming EP, 4U, which will also include "Rebel" and "We Ain't Worried." The singer last released So Amazin' in May 2006, which debuted at No. 11 on the Billboard 200 and features the single "Say I."