One miracle revealed eastern ruler (4)
I believe the answer is:
emir
'eastern ruler' is the definition.
(I've seen this before)
'one miracle revealed' is the wordplay.
'revealed' indicates the answer is hidden within the clue (I've seen 'revealing' mean this).
'EMIR' is hidden within 'one miracle'.
(Other definitions for emir that I've seen before include "Islamic ruler" , "Top man" , "Muslim ruler stuck in mire" , "Arab ruler" , "Ruler in the Middle East and mire" .)