Poem of fourteen lines (6)
I believe the answer is:
sonnet
'poem of fourteen lines' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for sonnet that I've seen before include "Poem of 14 lines - Shakespeare wrote lots" , "Shelley's Ozymandias, for example" , "Fourteen-line 11" , "Fourteen-lined verse" , "Short poem with 14 lines" .)