Only half right on half of epic poem (5)
I believe the answer is:
lyric
'poem' is the definition.
(lyric poem is a kind of poem)
'only half right on half of epic' is the wordplay.
'half' means to take half the letters.
'right' becomes 'r' (common abbreviation).
'on' means one lot of letters go next to another.
'half of' means to take half the letters.
'only' cut in half is 'ly'.
'epic' cut in half is 'ic'.
'ly'+'r'+'ic'='LYRIC'
(Other definitions for lyric that I've seen before include "Poem - verse - London theatre" , "One barred from native country" , "Airline" , "Words to a song" , "Of poetry that expresses thoughts and feelings" .)