One isn't surprised it wasn't a miracle (2,6)
I believe the answer is:
no wonder
'one isn't surprised it' is the definition.
I don't know anything about this answer so I cannot judge whether this works.
'wasn't a miracle' is the wordplay.
'wasn't' becomes 'no' (I can't explain this - if you can you should believe this answer much more).
'a miracle' becomes 'wonder' (I've seen this in another clue).
'no'+'wonder'='NO WONDER'
Can you help me to learn more?
(Other definitions for no wonder that I've seen before include "it isn't surprising" , "hardly unforeseen" , "hardly unexpected" .)