Metal cask gents moved (8)
I believe the answer is:
tungsten
'metal' is the definition.
(I know that tungsten is a type of metal)
'cask gents moved' is the wordplay.
'cask' becomes 'tun' (tun is a kind of cask).
'moved' indicates anagramming the letters.
'gents' with letters rearranged gives 'gsten'.
'tun'+'gsten'='TUNGSTEN'
(Other definitions for tungsten that I've seen before include "Snug tent (anag)" , "Hard metal used in steels" , "Wolfram" , "Hard malleable metal" , "Chemical element, symbol W" .)