At the back of this newspaper, out of date (6,3,5)
I believe the answer is:
behind the times
'out of date' is the definition.
(thesaurus)
'at the back of this newspaper' is the wordplay.
'at the back of' becomes 'behind' (I've seen this before).
'this newspaper' becomes 'thetimes' (I've seen this before).
'behind'+'thetimes'='BEHIND THE TIMES'
(Other definitions for behind the times that I've seen before include "no longer seen as old-fashioned" , "as Rupert Murdoch is?" , "where one may be silent at breakfast?" , "out of touch" , "not being updated?" .)