In sum, the outcome (5)
I believe the answer is:
total
This clue could be a double definition.
'in' is the first definition.
Both the definition and answer are adjectives. Perhaps they are linked in a way I don't understand?
'sum the outcome' is the second definition.
'total' can be an answer for 'sum' (synonyms). I'm not sure about the 'the outcome' bit.
Can you help me to learn more?
(Other definitions for total that I've seen before include "Come to" , "It might be grand" , "Entirety" , "Aggregate, sum" , "Completely destroy" .)