Article of faith I spoon-feed to fool with solemn declaration (12,4,2,6)
I believe the answer is:
presidential oath of office
Here is my best explanation:
'article of faith i spoon-feed to fool with solemn declaration' is the definition.
I can't judge whether this defines the answer.
'article of faith i spoon-feed to fool' is the subsidiary indication.
'to fool' indicates anagramming the letters.
'articleoffaithispoonfeed' is an anagram of 'presidentialoathofoffice'.