Strong metallic element (8)
I believe the answer is:
titanium
'strong metallic element' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for titanium that I've seen before include "it's "elementary"" , "Element 22, makes strong non-corroding alloys" , "Metallic element used in aircraft components" , "Strong light metal, Ti" , "Light strong metallic element used in aeroplane parts" .)