Epic work, one penned by rising artist (5)
I believe the answer is:
iliad
'epic work' is the definition.
(I've seen this before)
'one penned by rising artist' is the wordplay.
'one' becomes 'i' (Roman numeral).
'penned by' indicates putting letters inside (inserted letters are penned in).
'rising' is a reversal indicator (letters written upwards in a down clue).
'artist' becomes 'Dali' (Salvador Dali).
'dali' reversed gives 'ilad'.
'i' going inside 'ilad' is 'ILIAD'.
(Other definitions for iliad that I've seen before include "Work on war" , "Homer Trojan war epic" , "Classic" , "Epic poem attributed to Homer" , "LITERATURE" .)