Most intelligent 150 with the height of ambition (9)
I believe the answer is:
cleverest
'most intelligent' is the definition.
'150 with the height of ambition' is the wordplay.
'150' becomes 'cl'.
'with' says to put letters next to each other.
'the height of ambition' becomes 'everest'.
'cl'+'everest'='CLEVEREST'
(Other definitions for cleverest that I've seen before include "Smartest" , "Brighter than others" , "of superlative brilliance" , "most able" .)