Driving mechanism to sustain vendors with no restrictions (9)
I believe the answer is:
propeller
'driving mechanism' is the definition.
(I've seen this before)
'sustain vendors with no restrictions' is the wordplay.
'sustain' becomes 'prop' (I can't explain this - if you can you should give a lot more credence to this answer).
'vendors' becomes 'sellers' ('seller' can be a synonym of 'vendor').
'with no restrictions' says to take the centre.
The middle of 'sellers' is 'eller'.
'prop'+'eller'='PROPELLER'
'to' is the link.
Can you help me to learn more?
(Other definitions for propeller that I've seen before include "Airscrew" , "attachment on aircraft" , "Driving mechanism" , "Driver" , "It rotates to push against air or water" .)