Prevalent around valley (4)
I believe the answer is:
vale
'valley' is the definition.
('vale' can be a synonym of 'valley')
'prevalent around' is the wordplay.
'around' indicates the answer is hidden within the clue.
'VALE' is hidden in the letters of 'prevalent'.
(Other definitions for vale that I've seen before include "Cheers" , "Trough between ridges" , "Valley" , "Maida -, N. London area; farewell (archaic)" , "'''Sweet ... of Avoca, how calm could I rest'' (Moore) (4)'" .)