An Ireland revitalised: it's rousing stuff (9)
I believe the answer is:
adrenalin
'rousing stuff' is the definition.
The answer and definition can be both substances as well as being singular nouns.
Maybe you can see an association between them that I can't see?
'an ireland revitalised' is the wordplay.
'revitalised' indicates anagramming the letters.
'an'+'ireland'='anireland'
'anireland' anagrammed gives 'ADRENALIN'.
'it's' is the link.
Can you help me to learn more?
(Other definitions for adrenalin that I've seen before include "Stimulating hormone" , "Hormone that stimulates the nervous system" , "Metabolism-affecting hormone" , "Booster" , "Hormone affecting circulation and breathing" .)