Lines about classical theatre (5)
I believe the answer is:
odeon
'classical theatre' is the definition.
(I've seen this before)
'lines about' is the wordplay.
'lines' becomes 'ode' (lines of poetry).
'about' becomes 'on' (as in a book 'on' a certain topic).
'ode'+'on'='ODEON'
(Other definitions for odeon that I've seen before include "Greek music hall" , "Greek music theatre" , "Do one (anag)" , "Ancient Greek building for music" , "Greek venue" .)