Back again with several lines (7)
I believe the answer is:
reverse
'back' is the definition.
(back can mean to reverse)
'again with several lines' is the wordplay.
'again' becomes 're' (prefix meaning 'again').
'with' means one lot of letters go next to another.
'several lines' becomes 'verse' (lines of poetry. I am not sure about the 'several' bit.).
're'+'verse'='REVERSE'
Can you help me to learn more?
(Other definitions for reverse that I've seen before include "Upset" , "Backtrack" , "Tails (of a coin)" , "Do u-turn to reserve" , "Countermand" .)