Come out of space with short green bananas (6)
I believe the answer is:
'come out of' is the definition.
'space with short green bananas' is the wordplay.
'space' becomes 'em' (in typography, a space as wide as a letter 'm').
'with' means one lot of letters go next to another.
'short' means to remove the last letter.
'bananas' indicates anagramming the letters (informal term for mad).
'green' with its final letter removed is 'gree'.
'gree' with letters rearranged gives 'erge'.
(Other definitions for emerge that I've seen before include "(Of facts) become known" , "Suddenly appear" , "Develop" , "Come into view" , "Gradually come out" .)