College key (4)
I believe the answer is:
yale
This could be a double definition.
'college' is the first definition.
'key' is the second definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Maybe you can see an association between them that I can't see?
Can you help me to learn more?
(Other definitions for yale that I've seen before include "member of College League" , "Mass. university" , "Member of the 11 - type of lock" , "US university; lock" , "New Haven university" .)