Strange creed involves the French state (7)
I believe the answer is:
declare
'state' is the definition.
(declaring is a kind of stating)
'strange creed involves the french' is the wordplay.
'strange' is an anagram indicator.
'involves' indicates putting letters inside.
'the french' becomes 'la' ('the' in French).
'creed' is an anagram of 'decre'.
'decre' enclosing 'la' is 'DECLARE'.
(Other definitions for declare that I've seen before include "Aver, state" , "Make a statement, to customs perhaps" , "Announce 13 closed" , "Announce formally" , "State clearly, announce officially" .)