Capital sum for the college head (9)
I believe the answer is:
principal
This could be a double definition.
'capital sum' is the first definition.
'college head' is the second definition.
'principal' can be an answer for 'head' (principal can mean a head teacher). I am not sure about the 'college' bit.
'for the' acts as a link.
Can you help me to learn more?
(Other definitions for principal that I've seen before include "British civil servant" , "Chief, main" , "Capital, or debt, on which interest is calculated" , "First in order of importance" , "Head teacher, say" .)