Short extract from writer's exposition (5)
I believe the answer is:
terse
'short' is the definition.
(synonyms)
'extract from writer's exposition' is the wordplay.
'extract from' says the answer is hidden in the clue (some letters extracted from the clue).
'TERSE' can be found hidden inside 'writers exposition'.
(Other definitions for terse that I've seen before include "Short and sharp" , "Trees (anag.)" , "Sententious" , "Brusque among trees" , "Brief and to the point" .)