Casual professor needs a comfy seat (4,5)
I believe the answer is:
easy chair
'a comfy seat' is the definition.
(I've seen this before)
'casual professor' is the wordplay.
'casual' becomes 'easy' (similar in meaning).
'professor' becomes 'chair' (chair can mean a professorship).
'easy'+'chair'='EASY-CHAIR'
'needs' is the link.
(Other definitions for easy chair that I've seen before include "Item of furniture" , "Common room feature" , "It's comfortable to sit in - sounds like it" , "Comfortable upholstered seat" , "nice spot to be in" .)