Stupid people lacking college educator for ABC etc (4)
I believe the answer is:
keys
'abc etc' is the definition.
(A, B and C are musical keys)
'stupid people lacking college educator' is the wordplay.
'stupid people' becomes 'donkeys' (donkey can mean a stupid person).
'lacking' suggests deleting specific letters.
'college educator' becomes 'don' (term for an academic).
'donkeys' with 'don' taken out is 'KEYS'.
'for' is the link.
(Other definitions for keys that I've seen before include "Openers - low-lying islands" , "Lower House of the Isle of Man parliament" , "Lockers" , "'Unlockers'" , "A to G perhaps" .)