Established in Magaluf or Malaga (6)
I believe the answer is:
formal
'established' is the definition.
(thesaurus)
'in magaluf or malaga' is the wordplay.
'in' indicates the answer is hidden within the clue.
'FORMAL' is hidden in the letters of 'magaluf or malaga'.
(Other definitions for formal that I've seen before include "Cermonial, solemn" , "Stately or official" , "Done in accordance with etiquette" , "conventionally correct" , "stuffy" .)