Boy, ten, turned up poem (6)
I believe the answer is:
sonnet
'poem' is the definition.
(type of poem)
'boy ten turned up' is the wordplay.
'boy' becomes 'son' (synonyms).
'turned up' is a reversal indicator.
'ten' in reverse letter order is 'net'.
'son'+'net'='SONNET'
(Other definitions for sonnet that I've seen before include "Fourteen line poem" , "Shelley's Ozymandias, for example" , "A form of poetry" , "Poem of fourteen lines" , "Poem of 14 lines - Shakespeare wrote lots" .)