A part of poem, hostile (6)
I believe the answer is:
averse
'hostile' is the definition.
(I've seen this before)
'a part of poem' is the wordplay.
'part of poem' becomes 'verse' ('verse' is part of 'poem').
'a'+'verse'='AVERSE'
(Other definitions for averse that I've seen before include "Metal rod; card game" , "Antipathetic" , "A line of poetry is opposed" , "Unwilling or disinclined, perhaps to hard work" , "Strongly opposed (to something)" .)