Drunk has arrived -- ha! (2,5)
I believe the answer is:
so there
'ha' is the definition.
I don't know anything about this answer so I cannot judge whether this works.
'drunk has arrived' is the wordplay.
'drunk' becomes 'sot' (both can mean someone who drinks too much).
'has' says to put letters next to each other.
'arrived' becomes 'here' (I can't justify this - if you can you should give a lot more credence to this answer).
'sot'+'here'='SO THERE'
Can you help me to learn more?
(Other definitions for so there that I've seen before include "That will teach you!" , "Defiant words" , "I defy you" , "Defiant remark" , "Derisive expression" .)