Ergo (2,4)
'ergo' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for therefore that I've seen before include "Ergo" , "Consequently - for that reason" , "It follows" , "Thus" , "as result" .)
(Other definitions for as such that I've seen before include "in a particular capacity" , "in the manner described" , "Intrinsically" , "in that particular role" .)