Throttle component of carburettor again playing up (7)
I believe the answer is:
garotte
'throttle' is the definition.
(garotting is a kind of throttling)
'component of carburettor again playing up' is the wordplay.
'component of' says the answer is hidden in the clue (I've seen this in other clues).
'up' says the letters should be written in reverse (in down clue: letters go upwards).
'ettorag' can be found hidden inside 'carburettor again playing'.
'ettorag' backwards is 'GAROTTE'.
(Other definitions for garotte that I've seen before include "Facility to dispose of person" , "Kill by strangulation" , "Spanish method of execution" , "Strangle" , "throttle" .)