Lead-in for jet or prop (5)
I believe the answer is:
turbo
'lead-in for jet or prop' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for turbo that I've seen before include "source of power" , "Charger improves a car's power" , "Powerful device" , "motor" , "found in car" .)