All round sides of ship, unthinkable to chuck alien out (9)
I believe the answer is:
spherical
'all round' is the definition.
(I've seen this before)
I don't understand how the rest of the clue works.
(Other definitions for spherical that I've seen before include "Like a ball" , "Completely round" , "Ball shaped" , "Globe-shaped" , "Rotund" .)