No longer quoting what's stimulating (8)
I believe the answer is:
exciting
'stimulating' is the definition.
('excite' can be a synonym of 'stimulate')
'no longer quoting' is the wordplay.
'no longer' becomes 'ex' (prefix meaning former or onetime).
'quoting' becomes 'citing' ('cite' can be a synonym of 'quote').
'ex'+'citing'='EXCITING'
'what's' acts as a link.
(Other definitions for exciting that I've seen before include "moving" , "Arousing thrill or expectation" , "Exhilarating, stirring" , "Dramatic" , "stirring things up!" .)