Theoretical (8)
'theoretical' is the definition.
(synonyms)
This is the entire clue.
(Other definitions for abstract that I've seen before include "Kandinsky painting, for example?" , "Art form; remove" , "Take away - what can't be seen" , "Intangible" , "Summary; remove" .)
(Other definitions for academic that I've seen before include "This person may be a professor" , "Professor possibly" , "Scholarly or of a university" , "Theoretical or scholarly - often not practical" , "Scholarly: hypothetical" .)