Theoretical; summary (8)
I believe the answer is:
I believe this is a double definition.
'theoretical' is the first definition.
(similar in meaning)
'summary' is the second definition.
(I know that abstract is a type of summary)
(Other definitions for abstract that I've seen before include "Extract; summary" , "Remove - what isn't tangible" , "Brats act in non-concrete way" , "Rothko work?" , "Take away - what can't be seen" .)