Choke or accelerator (8)
I believe the answer is:
throttle
I believe this is a double definition.
'choke' is the first definition.
('throttle' can be a synonym of 'choke')
'accelerator' is the second definition.
('throttle' can be a synonym of 'accelerator')
'or' is the link.
(Other definitions for throttle that I've seen before include "what regulates flow of juice?" , "Strangle; regulator valve" , "Choke by pressure on the windpipe" , "Valve regulating volume of fuel and air" , "Strangulate" .)