Some lines beat Zulu in South Africa (6)
I believe the answer is:
stanza
'some lines' is the definition.
(group of lines in a poem)
'beat zulu in south africa' is the wordplay.
'beat' becomes 'tan' (I've seen this before).
'zulu' becomes 'Z' (phonetic alphabet: alpha, bravo, charlie etc.).
'in' indicates putting letters inside.
'south africa' becomes 'sa' (abbreviation).
'tan'+'z'='tanz'
'tanz' going inside 'sa' is 'STANZA'.
(Other definitions for stanza that I've seen before include "Poetic verse" , "Chunk of poetry" , "Group of lines of verse" , "Lines of poetry forming a pattern" , "Lines forming a unit of verse" .)