Course for 99 in college (6)
I believe the answer is:
policy
'course' is the definition.
(I have seen 'Course of action' mean 'policy' so perhaps 'course' could also mean 'policy')
'99 in college' is the wordplay.
'99' becomes 'IC' (Roman numerals).
'in' is an insertion indicator.
'college' becomes 'poly' (polytechnic).
'ic' inserted within 'poly' is 'POLICY'.
'for' is the link.
(Other definitions for policy that I've seen before include "Plan of action of organisation - honesty is the best one" , "Principle of action by an organization" , "Honesty is said to be the best one" , "Adopted principle" , "Course of action proposed in a political manifesto" .)