Metallic element used in aircraft components (8)
I believe the answer is:
titanium
'metallic element used in aircraft components' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for titanium that I've seen before include "Hard metal" , "Metallic element used in aircraft components" , "'Metallic element, Ti (8)'" , "Atomic no. 22" , "Element 22, makes strong non-corroding alloys" .)