Justin Timberlake is trying to leave things on a high note as he teases his first new solo music in six years — just months after Britney Spears’ memoir revealed shocking bombshells about the stars’ early aughts romance. On Friday, the “SexyBack” singer, 42, teased his new single, “Selfish,” in a video shared to Instagram featuring footage from rehearsals for a show he played at the Orpheum Theater in his hometown of Memphis that night. “So if I get jealous, I can’t help it. I want every bit of you, I guess I’m selfish,” the 10-time Grammy winner croons in the R&B track. Later on Friday, Timbe…