Intellectual supporting launch (8)
I believe the answer is:
profound
'intellectual' is the definition.
(thesaurus)
'supporting launch' is the wordplay.
'supporting' becomes 'pro' (I've seen this in other clues).
'launch' becomes 'found' (synonyms).
'pro'+'found'='PROFOUND'
(Other definitions for profound that I've seen before include "Deep; intense" , "showing great knowledge" , "Intellectually deep" , "unqualified" , "deeply intellectual" .)