Book Italian cathedral displayed around beginning of last month (9)
I believe the answer is:
duodecimo
'book' is the definition.
(I've seen this before)
'italian cathedral displayed around beginning of last month' is the wordplay.
'italian cathedral' becomes 'duomo' (Italian term for a cathedral).
'displayed around' means one lot of letters goes inside another.
'beginning of last month' becomes 'deci' (resembles Dec 1).
'duomo' placed around 'deci' is 'DUODECIMO'.
(Other definitions for duodecimo that I've seen before include "Size of book" , "scale of work?" , "small book" .)