Old country in Abyssinia is reportedly making a comeback (6)
I believe the answer is:
persia
'old country' is the definition.
(historical term for Iran)
'in abyssinia is reportedly making a comeback' is the wordplay.
'in' indicates a hidden word.
'making a comeback' is a reversal indicator.
'aisrep' is hidden in the letters of 'abyssinia is reportedly'.
'aisrep' written backwards gives 'PERSIA'.
(Other definitions for persia that I've seen before include "Old Iran" , "Former name of Iran" , "Old name for country at 25 Across" , "Iran, formerly" , "Old land" .)