Business degree causes deep sleep (4)
I believe the answer is:
coma
'deep sleep' is the definition.
(I've seen this before)
'business degree' is the wordplay.
'business' becomes 'co'.
'degree' becomes 'ma' (Master of Arts is a type of degree).
'co'+'ma'='COMA'
'causes' is the link.
(Other definitions for coma that I've seen before include "Deep trance" , "State of insensibility" , "Unconscious state" , "long sleep" , "State of deep (often prolonged) unconsciousness" .)