Festival conductor is out of control (7)
I believe the answer is:
haywire
'is out of control' is the definition.
(I've seen this before)
'festival conductor' is the wordplay.
'festival' becomes 'hay' (I can't explain this - if you can you should believe this answer much more).
'conductor' becomes 'wire' (wire is a kind of conductor).
'hay'+'wire'='HAYWIRE'
Can you help me to learn more?
(Other definitions for haywire that I've seen before include "Mad" , "Malfunctioning badly" , "Not working properly" , "Erratic (colloq.)" , "nuts" .)