Scholar is purely theoretical (8)
I believe the answer is:
academic
I believe this clue is a double definition.
'scholar' is the first definition.
(I've seen this before)
'purely theoretical' is the second definition.
(I've seen this in another clue)
'is' is the link.
(Other definitions for academic that I've seen before include "Associated with places of higher learning" , "Relating to scholarship and education" , "Scholarly: hypothetical" , "Theoretical or relating to colleges" , "Scholarly - unrealistic" .)