Shakespearean verse (6)
I believe the answer is:
sonnet
'shakespearean verse' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for sonnet that I've seen before include "14-line poem" , "Fourteen-line 11" , "14-line verse" , "The poem was sent on" , "Poem of fourteen lines" .)