Plaintive poem (5)
I believe the answer is:
elegy
'plaintive poem' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for elegy that I've seen before include "Poetic lament for the dead" , "Dirge" , "A sorrowful poem like Gray's" , "Poem lamenting the dead" , "lines of regret" .)