Sea-fog initially hated at all resorts (4)
I believe the answer is:
haar
'sea-fog' is the definition.
(I've seen this before)
'initially hated at all resorts' is the wordplay.
'initially' indicates taking the first letters.
The initial letters of 'hated at all resorts' is 'HAAR'.
(Other definitions for haar that I've seen before include "East-coast sea fog" , "chilly sea-mist" , "Sea-fog" , "Sea mist" , "Raw sea-mist" .)