Love names included in prescribed poem (6)
I believe the answer is:
sonnet
'poem' is the definition.
(type of poem)
'love names included in prescribed' is the wordplay.
'love' becomes 'o' (love means zero in tennis).
'names' becomes 'nn' (abbreviation for 'name' twice).
'included in' is an insertion indicator.
'prescribed' becomes 'set' (set can mean pre-determined or prescribed).
'o'+'nn'='onn'
'onn' put inside 'set' is 'SONNET'.
(Other definitions for sonnet that I've seen before include "Tonnes (anag.)" , "Poem of fourteen lines" , "The poem was sent on" , "Shelley's Ozymandias, for example" , "Fourteen-line poem" .)