Revision of simple bios that's out of the question (10)
I believe the answer is:
impossible
'out of the question' is the definition.
('impossible' can be a synonym of 'out of the question')
'revision of simple bios' is the wordplay.
'revision of' is an anagram indicator.
'simple'+'bios'='simplebios'
'simplebios' with letters rearranged gives 'IMPOSSIBLE'.
'that's' acts as a link.
(Other definitions for impossible that I've seen before include "Not able to take place" , "Hopeless" , "Not able to exist" , "See 14 down" , "See 10" .)