Wheel turned round, operating explosive device (9)
I believe the answer is:
detonator
'explosive device' is the definition.
(I know that detonator is a type of explosive device)
'wheel turned round operating' is the wordplay.
'wheel' is a reversal indicator (I've seen 'wheeled' mean this (letters are wheeled back)).
'turned' becomes 'rotated' (similar in meaning).
'round' means one lot of letters goes inside another.
'operating' becomes 'on' (I've seen this in other clues).
'rotated' in reverse letter order is 'detator'.
'detator' placed around 'on' is 'DETONATOR'.
(Other definitions for detonator that I've seen before include "means to cause explosion" , "One sets off bang" , "Explosion starter" , "Device for setting off a bomb" , "cap" .)