Expression of defiance (2,5)
I believe the answer is:
so there
'expression of defiance' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for so there that I've seen before include "What are you going to do about that" , "Defiant statement" , "Triumphant put-down" , "message of defiance" , "Derisive expression" .)