Beginning at home one ordeal without second of trauma (7)
I believe the answer is:
initial
'beginning' is the definition.
(I've seen this before)
'home one ordeal without second of trauma' is the wordplay.
I cannot really understand how this works, but
'home' could be 'in' ('he's home' can mean 'he's in') and 'in' is found within the answer.
'one' could be 'i' (Roman numeral) and 'i' is present in the answer.
This may be the basis of clue (or it may be nonsense).
'at' is the link.
(Other definitions for initial that I've seen before include "Occurring at the beginning" , "Word's first letter" , "Occurring at the start" , "write two or three letters, usually" , "Original; beginning" .)