Correct to ring head of Charolais bull (5)
I believe the answer is:
edict
'bull' is the definition.
(thesaurus)
'correct to ring head of charolais' is the wordplay.
'correct' becomes 'edit' (I've seen this before).
'to ring' means one lot of letters goes inside another.
'head of' suggests taking the first letters.
The initial letter of 'charolais' is 'c'.
'edit' placed around 'c' is 'EDICT'.
(Other definitions for edict that I've seen before include "Decree by authority" , "Official order" , "Proclamation, law" , "Legally-binding order" , "Order issued by an authority" .)