Diana's account causing amusement (9)
I believe the answer is:
diversion
'amusement' is the definition.
(I've seen this before)
'diana's account' is the wordplay.
'diana' becomes 'Di' (Di is short for Diana).
'account' becomes 'version' (version is a kind of account).
'di'+'version'='DIVERSION'
'causing' acts as a link.
(Other definitions for diversion that I've seen before include "Detour" , "Alternative route" , "Amusement -- temporary redirection" , "entertainment" .)