Belief in direct action (6)
I believe the answer is:
credit
'belief' is the definition.
(thesaurus)
'direct action?' is the wordplay.
'action?' indicates an anagram (I've seen 'action' mean this).
'direct' anagrammed gives 'CREDIT'.
'in' is the link.
(Other definitions for credit that I've seen before include "Arrangement for deferred payment" , "Good reputation; tick" , "good character" , "Favourable balance - good repute" , "Believe - one side of an account" .)