Writer fed up with a piece of poetry (5)
I believe the answer is:
defoe
'writer' is the definition.
(Daniel Defoe)
'fed up with a piece of poetry' is the wordplay.
'up' says the letters should be written backwards (in down clue: letters go upwards).
'with' means one lot of letters go next to another.
'a piece of poetry' becomes 'oe' (I can't explain this - if you can you should give a lot more credence to this answer).
'fed' written backwards gives 'def'.
'def'+'oe'='DEFOE'
Can you help me to learn more?
(Other definitions for defoe that I've seen before include "18th-century author" , "Author of Robinson Crusoe, d. 1731" , "Daniel . . . . . wrote ''Robinson Crusoe'' (5)" , "Gulliver author" , "Daniel, writer, d. 1731" .)