Break up with Spooner’s tetchy American girlfriend (9)
I believe the answer is:
dissipate
'break up' is the definition.
(synonyms)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for dissipate that I've seen before include "Be dispelled/dispersed" , "drive away" , "Exhaust" , "scatter" , "Fritter away" .)