Form of armour (5,4)
I believe the answer is:
chain mail
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">form of armour</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I know that chain mail is a type of suit of armour)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for chain mail that I've seen before include "guard" , "Armour with tiny metal rings" , "defensive link-up" , "Cover protecting old soldier" , "Armour of small metal links" .)