Without leader, orchestra try to keep right tempo (7)
I believe the answer is:
allegro
'tempo' is the definition.
(allegro is a kind of tempo)
'without leader orchestra try to keep right' is the wordplay.
'without leader' means to remove the first letter.
'orchestra' becomes 'halle' (The Halle, UK symphony orchestra).
'try' becomes 'go' (both can mean an attempt).
'to keep' indicates putting letters inside.
'right' becomes 'r' (common abbreviation).
'halle' with its first letter removed is 'alle'.
'go' placed around 'r' is 'gro'.
'alle'+'gro'='ALLEGRO'
(Other definitions for allegro that I've seen before include "Brisk mus. speed" , "Brisk musical piece" , "Moving fast" , "Austin" , "musical term" .)