Faithful man of God admits brief deception (6)
I believe the answer is:
strict
'faithful' is the definition.
(thesaurus)
'man of god admits brief deception' is the wordplay.
I cannot really understand how this works, but
'man' could be 'ric' and 'ric' is found in the answer.
This may be the basis of clue (or it may be nonsense).
(Other definitions for strict that I've seen before include "Allowing no laxness" , "Hard" , "Severe and unyielding" , "Excessive pride" , "Severe, stern" .)