Support trader bringing out first mechanical component (9)
I believe the answer is:
propeller
'mechanical component' is the definition.
'support trader bringing out first' is the wordplay.
'support' becomes 'prop' (prop is a kind of support).
'trader' becomes 'seller' (I've seen this before).
'bringing out first' means to remove the first letter (the first letter is brought out of the word).
'seller' with its initial letter taken off is 'eller'.
'prop'+'eller'='PROPELLER'
(Other definitions for propeller that I've seen before include "Mechanical device" , "Driver" , "Airscrew" , "Driving mechanism" , "attachment on aircraft" .)