Early locomotive leaves (6)
I believe the answer is:
rocket
This clue is a double definition.
'early locomotive' is the first definition.
(Stephenson's Rocket, steam locomotive)
'leaves' is the second definition.
(I've seen this before)
(Other definitions for rocket that I've seen before include "It is used to propel a spacecraft or missile" , "Firework and salad ingredient" , "Structure that flies by expelling gases - or a reprimand" , "It's propelled to a great height by combustion" , "Severe reprimand" .)