Sweetheart having returned, excitement ultimately rising (6)
I believe the answer is:
revolt
'rising' is the definition.
(rising can mean a revolt or rebellion)
'sweetheart having returned excitement ultimately' is the wordplay.
'sweetheart' becomes 'lover' (sweetheart can mean a lover).
'having returned' shows that the letters should be reversed in order.
'excitement ultimately' becomes 't' (I am not sure about this - if you are sure you should believe this answer much more).
'lover' back-to-front is 'revol'.
'revol'+'t'='REVOLT'
Can you help me to learn more?
(Other definitions for revolt that I've seen before include "Don't hurry" , "Rebel or disgust" , "Uprising, insurrection" , "Cause to feel disgust" , "Organised opposition to authority" .)