Expels (5)
'expels' is the definition.
('oust' can be a synonym of 'expel')
This is all the clue.
(Other definitions for ousts that I've seen before include "Unseats, puts out of office" , "Replaces" , "Supplants" , "Ejects, expels" , "Forces someone out and takes their place" .)
(Another definition for spews that I've seen is " Vomits or emits in stream".)