Boss promises to pay intellectual (8)
I believe the answer is:
studious
'intellectual' is the definition.
'boss promises to pay' is the wordplay.
'boss' becomes 'stud' (both can mean a metal decoration).
'promises to pay' becomes 'IOU's' (promises to pay a debt).
'stud'+'ious'='STUDIOUS'
(Other definitions for studious that I've seen before include "reading a lot" , "Like a good schoolboy" , "Devoted to learning; deliberate" , "Given to serious reading" , "showing diligence" .)