Curse loud fools for being gullible (9)
I believe the answer is:
credulous
'being gullible' is the definition.
(I've seen this before)
'curse loud fools' is the wordplay.
'fools' indicates anagramming the letters (I've seen this in other clues).
'curse'+'loud'='curseloud'
'curseloud' with letters rearranged gives 'CREDULOUS'.
'for' is the link.
(Other definitions for credulous that I've seen before include "Likely to believe" , "Gullible" , "Apt to believe without sufficient evidence" , "Easily fooled" , "Too ready to believe things" .)