Protective cover (6)
(Other definitions for casing that I've seen before include "Recceing" , "Protective covering as of engine" , "Outside cover" , "Outer covering of something" , "This gives protection" .)
(Other definitions for armour that I've seen before include "Chain mail, e.g." , "Soldier's body protection" , "Metal or chainmail suit" , "Protective covering made of metal" , "Greave, sallet and cuirass are pieces of this" .)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">protective cover?</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for alias that I've seen before include "Pseudonym" , "Also known as" , "Alternative name" , "False identity" , "aka" .)