Radical in favour of institute (8)
I believe the answer is:
profound
'radical' is the definition.
(thesaurus)
'in favour of institute' is the wordplay.
'in favour of' becomes 'pro' (being pro a particular cause).
'institute' becomes 'found' (synonyms).
'pro'+'found'='PROFOUND'
(Other definitions for profound that I've seen before include "anything but superficial" , "unqualified" , "Intellectually deep" , "Far-reaching" , "Needing deep thought" .)