Arrive with empty diary - that's funny (6)
I believe the answer is:
comedy
'that's funny' is the definition.
I can't judge whether this definition defines the answer.
'arrive with empty diary' is the wordplay.
'arrive' becomes 'come' (coming is a kind of arriving).
'with' means one lot of letters go next to another.
'empty' says to hollow out the word (remove centre letters).
'diary' with its middle removed is 'dy'.
'come'+'dy'='COMEDY'
Can you help me to learn more?
(Other definitions for comedy that I've seen before include "Funny and/or happy play" , "A funny play or farce" , "farce, perhaps" , "Dante wrote ''The Divine . . . . . .''" , "Humour" .)