Gush like a geyser (4)
I believe the answer is:
spew
'gush like a geyser' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for spew that I've seen before include "Vomit (colloq.)" , "Be expelled rapidly in large quantities" , "issue" , "Money (slang)" , "Be sick" .)