Armor-plated (8)
I believe the answer is:
ironclad
'armor-plated' is the definition.
(thesaurus)
This is the entire clue.
(Other definitions for ironclad that I've seen before include "Unassailable" , "monitor, for example" , "Old cairn with metal protection" , "Vessel well protected" , "Well protected, like armoured alibi" .)