Hot wing from takeaway is fairly mild (8)
I believe the answer is:
harmless
'mild' is the definition.
(thesaurus)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for harmless that I've seen before include "Completely safe" , "Causing no damage" , "Benign, innocuous" , "Not likely to cause damage" , "Safe; innocent" .)