。
Don't skip out on the concert.
Literal
Concert [obj-を] sneak-away-do [don't-な] [emph-よ].
ドロンする is a colloquial/dated slang expression meaning 'to slip away / abscond,' derived from the stage effect ドロン — the drum sound and smoke that accompanied a ninja's disappearing act in kabuki theater. ~するな is the prohibitive command. The trailing よ softens the prohibition slightly into a warning between friends.