Shade, metallic grey, oddly (5)
I believe the answer is:
tinge
'shade' is the definition.
(tinge is a kind of shade)
'metallic grey oddly' is the wordplay.
'metallic' becomes 'tin'.
'oddly' means one should take alternating letters.
The alternating letters of 'grey' are 'ge'.
'tin'+'ge'='TINGE'
(Other definitions for tinge that I've seen before include "A smack" , "Colour slightly; trace" , "Little bit of colour" , "show a bit of colour ?" , "Small quantity of (differing) colour" .)