Street areas linked by southern land lines (6)
I believe the answer is:
stanza
'lines' is the definition.
(group of lines in a poem)
'street areas linked by southern land' is the wordplay.
'street' becomes 'st' (abbreviation).
'areas' becomes 'aa' (an abbreviation for area written twice).
'linked by' indicates putting letters inside (some letters come between or join together others).
'southern land' becomes 'NZ' (New Zealand).
'aa' placed around 'nz' is 'anza'.
'st'+'anza'='STANZA'
(Other definitions for stanza that I've seen before include "Section of verse" , "Poetic unit" , "Chunk of poetry" , "Fixed number of lines of verse" , "Part of a poem" .)