State that's back in within a month (4)
I believe the answer is:
oman
'state' is the definition.
(Oman is an example)
'back in within a month' is the wordplay.
'back' is a reversal indicator.
'in' says the answer is hidden in the clue.
'namo' is hidden within 'within a month'.
'namo' written backwards gives 'OMAN'.
'that's' is the link.
(Other definitions for oman that I've seen before include "Muscat's country" , "Land" , "Sultanate, capital Muscat" , "monarchy" , "Former Gulf country, Muscat and --" .)