Hard to believe (10)
'hard to believe' is the definition.
(thesaurus)
This is the entire clue.
(Other definitions for incredible that I've seen before include "Beyond belief" , "Impossible to believe" , "Unbelievable" , "Fantastic" .)
(Other definitions for fishy that I've seen before include "As smelt, perhaps" , "Suspicious in piscine way" , "Ray is so" , "Suspect" , "Questionable" .)