No medic turned out to be fiendish (7)
I believe the answer is:
demonic
'to be fiendish' is the definition.
(synonyms)
'no medic turned' is the wordplay.
'turned' is an anagram indicator.
'no'+'medic'='nomedic'
'nomedic' is an anagram of 'DEMONIC'.
'out' is the link.
(Other definitions for demonic that I've seen before include "Fiendish or satanic" , "Dime con (anag.)" , "Inspired as if by a fiend" , "diabolical" , "Devilish" .)