Readmit city, oddly absent in decree (5)
I believe the answer is:
edict
'decree' is the definition.
(synonyms)
'readmit city oddly absent' is the wordplay.
'oddly absent' means one should take alternating letters (odd-numbered letters removed).
'readmit'+'city'='readmitcity'
The alternating letters of 'readmitcity' are 'EDICT'.
'in' acts as a link.
(Other definitions for edict that I've seen before include "Injunction" , "Canon" , "Order issued by an authority" , "Authoritative decree" , "An official command" .)