Bleeping alarm has a function (4)
I believe the answer is:
gala
'a function' is the definition.
(thesaurus)
'bleeping alarm has' is the wordplay.
'has' says the answer is hidden in the clue.
'GALA' is hidden in the letters of 'bleeping alarm'.
(Other definitions for gala that I've seen before include "Swimming competition" , "Public party" , "Sports meeting" , "Festive occasion - variety of apple" , "Festival" .)