Thus drinking in break on island republic (9)
I believe the answer is:
singapore
'island republic' is the definition.
Although both the answer and definition are singular nouns, I don't understand how they can define each other.
'thus drinking in break' is the wordplay.
'thus' becomes 'sore' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'drinking' is an insertion indicator.
'break' becomes 'gap' ('gap' can be a synonym of 'break').
'in'+'gap'='ingap'
'sore' enclosing 'ingap' is 'SINGAPORE'.
'on' is the link.
Can you help me to learn more?
(Other definitions for singapore that I've seen before include "Commonwealth city state" , "part of Asia" , "Asian republic" , "Asian country, capital and mega-port" , "Foreign capital" .)