Less than half of characters in college pass (3)
I believe the answer is:
col
'pass' is the definition.
(col is a term for a mountain pass)
'less than half of characters in college' is the wordplay.
'less than half' becomes 'co' (I can't justify this - if you can you should believe this answer much more).
'of characters in' says to take the centre (I've seen 'characters in' mean this).
The middle of 'college' is 'l'.
'co'+'l'='COL'
(Other definitions for col that I've seen before include "Somewhere up on the mountain" , "Young horse almost" , "dip?" , "Pass between hills" , "Officer" .)