Brazilian capital essentially dynamises province (5)
I believe the answer is:
realm
'province' is the definition.
(I've seen this before)
'brazilian capital essentially dynamises' is the wordplay.
'brazilian capital' becomes 'real' (Brazilian currency - 'capital' can mean money).
'essentially' says to take the centre.
The central letter of 'dynamises' is 'm'.
'real'+'m'='REALM'
(Other definitions for realm that I've seen before include "A Nation" , "Kingdom, domain" , "Peers are possessed by this" , "Area of interest/activity" , "World" .)