Lines up one to head paper round (3)
I believe the answer is:
ode
'lines' is the definition.
(lines of poetry)
'up one to head paper round' is the wordplay.
'up' says the letters should be written backwards (in down clue: letters go upwards).
'one to head paper' becomes 'ed' (I can't justify this - if you can you should give a lot more credence to this answer).
'round' becomes 'o' (o is a circular letter).
'ed'+'o'='edo'
'edo' back-to-front is 'ODE'.
Can you help me to learn more?
(Other definitions for ode that I've seen before include "Literary work" , "A poem celebrating person or event" , "- - to a 12 Urn" , "(Railway)system" , "poetry" .)