Idiot runs show behind screens (5)
I believe the answer is:
moron
'idiot' is the definition.
(I know that idiot can be written as moron)
'runs show behind screens' is the wordplay.
'runs' becomes 'r' (abbreviation in cricket).
'show behind' becomes 'moon' (moon can mean to show one's bottom).
'screens' means one lot of letters goes inside another (screen can mean to cover up).
'r' put into 'moon' is 'MORON'.
(Other definitions for moron that I've seen before include "Cretin" , "Somewhat feeble-minded person" , "Complete imbecile" , "Simpleton" , "Person of subnormal intelligence" .)