Protecting area, utterly stupid guards (8)
I believe the answer is:
tutelary
'protecting' is the definition.
(thesaurus)
'area utterly stupid guards' is the wordplay.
'area' becomes 'a' (maths abbreviation).
'stupid' indicates anagramming the letters (in a stupid order).
'guards' is an insertion indicator.
'utterly' with letters rearranged gives 'tutelry'.
'a' going into 'tutelry' is 'TUTELARY'.
(Other definitions for tutelary that I've seen before include "Serving as guardian, giving protection" , "Like the Guardian" .)