I am to settle in instant (9)
I believe the answer is:
immediate
'instant' is the definition.
(I've seen this in another clue)
'i am to settle' is the wordplay.
'i am' becomes 'I'm' (contraction).
'to settle' becomes 'mediate' (mediating is a kind of settling).
'im'+'mediate'='IMMEDIATE'
'in' acts as a link.
(Other definitions for immediate that I've seen before include "Most urgent; current" , "Occurring without delay" , "Present" , "on the spot" , "Prompt,straightaway" .)