Claim fast is fun (8)
I believe the answer is:
pleasure
'is fun' is the definition.
(thesaurus)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for pleasure that I've seen before include "Urgent entreaty begins gratification" , "Happy satisfaction" , "Enjoyment, happiness" , "Gratification of the senses" , "amusement" .)