Dad upset friend, creating shock (5)
I believe the answer is:
appal
'shock' is the definition.
(I know that shock can be written as appal)
'dad upset friend' is the wordplay.
'dad' becomes 'pa' (both can mean one's father).
'upset' shows that the letters should be reversed in order.
'friend' becomes 'pal' (pal can mean a friend).
'pa' backwards is 'ap'.
'ap'+'pal'='APPAL'
'creating' is the link.
(Other definitions for appal that I've seen before include "Greatly horrify" , "Dismay, horrify" , "Cause to be unpleasantly surprised" , "Scandalise" , "expressed dismay" .)