Extract of essay on Arabic is so long (8)
I believe the answer is:
sayonara
'is so long' is the definition.
(I've seen this before)
'extract of essay on arabic' is the wordplay.
'extract of' says the answer is hidden in the clue (I've seen this in other clues).
'SAYONARA' can be found hidden inside 'essay on arabic'.
(Other definitions for sayonara that I've seen before include "So long" , "Japanese goodbye" , "Goodbye or farewell in Japan" , "Japanese farewell" , "Goodbye (Jap.)" .)