Run musical drama, extremely tiresome (7)
I believe the answer is:
operate
'run' is the definition.
(I know that run can be written as operate)
'musical drama extremely tiresome' is the wordplay.
'musical drama' becomes 'opera' (I've seen this before).
'extremely' means to remove the middle letters (only the extremes of the word are used).
'tiresome' with its centre removed is 'te'.
'opera'+'te'='OPERATE'
(Other definitions for operate that I've seen before include "Work - perform surgery" , "Eat rope (anag.)" , "Control, run, a machine say" , "(Of machine) function" , "Work, run" .)