Wrote up numbers after a round number of fourteen lines? (6)
I believe the answer is:
sonnet
'fourteen lines?' is the definition.
'sonnet' can be an answer for 'lines?' (poem of 14 lines). I am not sure about the 'fourteen' bit.
'wrote up numbers after a round number' is the wordplay.
'wrote up' shows that the letters should be reversed in order.
'numbers' becomes 'nos' (no. is a kind of number).
'after' is a charade indicator (letters next to each other).
'a round number' becomes 'ten' (I've seen this in another clue).
'nos' after 'ten' is 'tennos'.
'tennos' back-to-front is 'SONNET'.
'of' is the link.
Can you help me to learn more?
(Other definitions for sonnet that I've seen before include "14-line verse" , "Sent on the verse form" , "Fourteen-lined poem" , "Fourteen-line poem" , "Shakespearean poem" .)