Prudence, maybe, is no credit (10)
I believe the answer is:
discretion
'prudence' is the definition.
(synonyms)
'maybe is no credit' is the wordplay.
'maybe' indicates an anagram.
'is'+'no'+'credit'='isnocredit'
'isnocredit' anagrammed gives 'DISCRETION'.
(Other definitions for discretion that I've seen before include "Diplomacy" , "Tactful quality" , "The better part of valour" , "Freedom to decide on an action" , "Tact - prudence" .)