Mechanism making the cart wobbly (7)
I believe the answer is:
ratchet
'mechanism' is the definition.
(ratchet is a kind of mechanism)
'the cart wobbly' is the wordplay.
'wobbly' indicates anagramming the letters.
'the'+'cart'='thecart'
'thecart' with letters rearranged gives 'RATCHET'.
'making' is the link.
(Other definitions for ratchet that I've seen before include "One-way-motion toothed wheel" , "this will stop revolutionary backsliding" , "Device stopping backward movement" , "Bar that fits into the notches of a toothed wheel" , "One-way toothed wheel" .)