A section of the strongest Anzac lines (6)
I believe the answer is:
stanza
'a section' is the definition.
(I have seen 'Section of poem ' mean 'stanza' so perhaps 'section' could also mean 'stanza')
'of the strongest anzac lines' is the wordplay.
'of' says the answer is hidden in the clue.
'STANZA' can be found hidden inside 'strongest anzac lines'.
(Other definitions for stanza that I've seen before include "Poetic unit" , "Part of a poem" , "A verse of poetry" , "Group of poetic lines" , "Lines forming a unit of verse" .)