It helps to stop getting muscles (3)
I believe the answer is:
abs
This clue is a double definition.
'it helps to stop' is the first definition.
(short for anti-lock braking system)
'muscles' is the second definition.
(I've seen this before)
'getting' acts as a link.
(Other definitions for abs that I've seen before include "ratings?" , "Exercise to improve these" , "stopping system" , "Some musculature" , "Stomach muscles (abbr)" .)