Belief almost widely prevalent in holiday destination (8)
I believe the answer is:
tenerife
'holiday destination' is the definition.
(Canary Island)
'belief almost widely prevalent' is the wordplay.
'belief' becomes 'tenet' (synonyms).
'almost' means to remove the last letter (most of the word but not all of it).
'widely prevalent' becomes 'rife' (I've seen this in another clue).
'tenet' with its last letter removed is 'tene'.
'tene'+'rife'='TENERIFE'
'in' is the link.
(Other definitions for tenerife that I've seen before include "Popular holiday destination" , "Fire teen off the island" , "There's an odd inter fee on the island" , "Largest of the Canary Islands" , "holiday island" .)