Writer’s epigram, not entirely to the point (5)
I believe the answer is:
terse
'to the point' is the definition.
(synonyms)
'writer's epigram not entirely' is the wordplay.
'not entirely' says the answer is hidden in the clue.
'TERSE' is hidden within 'writers epigram'.
(Other definitions for terse that I've seen before include "Curt among trees" , "Short and sharp" , "Succinct about trees" , "Curtly brief" , "Briefly expressed" .)