For Penn and Teller, according to Carroll, it's a driving mechanism (9)
I believe the answer is:
propeller
'a driving mechanism' is the definition.
(I've seen this before)
'for penn and teller according to carroll it's' is the wordplay.
I cannot really see how this works, but
'for' could be 'pro' (as in being 'pro' something) and 'pro' is found within the answer.
'it' could be 'e' ('e' can mean 'electronic' which is similar to 'IT') and 'e' is found within the answer.
This explanation may well be incorrect...
(Other definitions for propeller that I've seen before include "Driving mechanism" , "Mechanical device" , "Airscrew" , "Screw (on a boat)" , "Driver" .)