Come up with component for main ventilator (6)
I believe the answer is:
invent
'come up with' is the definition.
(I've seen this in another clue)
'component for main ventilator' is the wordplay.
'component' indicates the answer is hidden within the clue (I've seen 'component of' mean this (I've seen this in other clues)).
'INVENT' is hidden within 'for main ventilator'.
(Other definitions for invent that I've seen before include "Think up, create" , "Originate" , "Design for the first time" , "Conceive" , "Come up with" .)