Macho guy promises on paper to be intellectual? (8)
I believe the answer is:
studious
'be intellectual?' is the definition.
'macho guy promises on paper' is the wordplay.
'macho guy' becomes 'stud' (I've seen this in another clue).
'promises on paper' becomes 'ious' (I've seen this in another clue).
'stud'+'ious'='STUDIOUS'
'to' acts as a link.
(Other definitions for studious that I've seen before include "working hard" , "Thoughtful - hard-working" , "Diligent, assiduous" , "with great care" , "reading a lot" .)