Poem about child on web.. (6)
I believe the answer is:
sonnet
'poem' is the definition.
(type of poem)
'child on web' is the wordplay.
'child' becomes 'son' (male child).
'on' is a charade indicator (letters next to each other) (in a down clue, letters appear on others).
'web' becomes 'net' (synonyms).
'son'+'net'='SONNET'
'about' is the link.
(Other definitions for sonnet that I've seen before include "Shelley's Ozymandias, for example" , "Fourteen-lined verse" , "The poem was sent on" , "Poetic fourteen-liner" , "Shakespearean poem" .)