Think about new sin in revised credo (8)
I believe the answer is:
consider
'think about' is the definition.
(considering is a kind of thinking about)
'new sin in revised credo' is the wordplay.
'new' indicates anagramming the letters.
'in' indicates putting letters inside.
'revised' indicates an anagram.
'sin' anagrammed gives 'nsi'.
'credo' anagrammed gives 'coder'.
'nsi' put within 'coder' is 'CONSIDER'.
(Other definitions for consider that I've seen before include "Ponder on" , "Give thought to" , "Deem to be, believe" , "Hold" , "Muse, mull over" .)