Practice session (4-2)
'practice session' is the definition.
(rehearsal is a kind of practice session)
This is the entire clue.
(Other definitions for rehearsal that I've seen before include "Practice session in preparation for public performance" , "show trial" , "Preparation for a show" , "Drill" , "Practice - run-through" .)
(Other definitions for warm-up that I've seen before include "Preparatory exercises before an event" , "Prepare for athletic exercise" , "Preliminary exercise" , "Muscle-loosening pre-sport activity" , "Athlete's preparation" .)