Graduate smashed train from another planet (7)
I believe the answer is:
martian
'from another planet' is the definition.
(from Mars)
'graduate smashed train' is the wordplay.
'graduate' becomes 'ma' (abbreviation for Master of Arts).
'smashed' indicates anagramming the letters.
'train' anagrammed gives 'rtian'.
'ma'+'rtian'='MARTIAN'
(Other definitions for martian that I've seen before include "Sci-fi alien" , "Invader in The War of the Worlds (H. G. Wells)" , "seeing little green man?" , "Being from another planet" , "Relating to a particular planet" .)