Back issue by Sunday newspaper (5)
I believe the answer is:
times
'newspaper' is the definition.
'back issue by sunday' is the wordplay.
'back' is a reversal indicator.
'issue' becomes 'emit' (I've seen this before).
'by' is a charade indicator (letters next to each other).
'sunday' becomes 's'.
'emit' reversed gives 'time'.
'time'+'s'='TIMES'
(Other definitions for times that I've seen before include "Paces" , "''For the ..., they are a'changin'''(Bob Dylan)" , "operator" , "- - they are a-changin'" , "See 10" .)