For the intelligent, full of promise (6)
I believe the answer is:
bright
I believe this clue is a triple definition!
'for the intelligent' is the first definition.
(thesaurus)
'full' is the second definition.
(thesaurus)
'of promise' is the third definition.
(thesaurus)
(Other definitions for bright that I've seen before include "Clever; fine" , "Shining; intelligent" , "Clear" , "Intelligent - glaring" , "Cheerful or quick-witted" .)