Intellectual — scientist (6)
I believe the answer is:
boffin
I believe this is a double definition.
'intellectual' is the first definition.
(boffin is a kind of intellectual)
'scientist' is the second definition.
(boffin can informally mean a scientist)
(Other definitions for boffin that I've seen before include "Military scientist" , "Back-room boy" , "Technical expert" , "Research scientist" , "Brainbox" .)