'Sun' with dire spread guaranteed (7)
I believe the answer is:
insured
'guaranteed' is the definition.
(insuring is a kind of guaranteeing)
'sun with dire spread' is the wordplay.
'with' is a charade indicator (letters next to each other).
'spread' indicates an anagram.
'sun' after 'dire' is 'diresun'.
'diresun' with letters rearranged gives 'INSURED'.
(Other definitions for insured that I've seen before include "Covered for loss" , "Covered for losses" , "Protected against risk" , "Financially covered" , "Financially protected" .)