The republic was once in. In a time of revolution (7)
I believe the answer is:
dahomey
'the republic was once' is the definition.
I can't tell whether this definition defines the answer.
'in a time of revolution' is the wordplay.
'in' indicates putting letters inside.
'a time' becomes 'day' (day is a kind of time).
'of revolution' becomes 'home' (I can't justify this - if you can you should believe this answer much more).
'day' placed around 'home' is 'DAHOMEY'.
'in' is the link.
Can you help me to learn more?
(Other definitions for dahomey that I've seen before include "old African country" , "Benin some time ago" , "Former name of Benin; O my head (anag.)" .)