It's not difficult for the professor to get this - as for the rest? (4,5)
I believe the answer is:
easy chair
'get this as for the rest?' is the definition.
Although both the answer and definition are singular nouns, I don't see how they can define each other.
'it's not difficult for the professor' is the wordplay.
'it's not difficult' becomes 'easy' ('easy' is the opposite to 'difficult').
'for' means one lot of letters go next to another.
'the professor' becomes 'chair' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'easy'+'chair'='EASY CHAIR'
'to' is the link.
Can you help me to learn more?
(Other definitions for easy chair that I've seen before include "Comfortable upholstered seat" , "It's comfortable to sit in - sounds like it" , "It's not hard to sit in" , "comfortable position" , "source of comfort" .)