Last metal: it gets processed after uranium (8)
I believe the answer is:
ultimate
'last' is the definition.
(similar in meaning)
'metal it gets processed after uranium' is the wordplay.
'gets processed' is an anagram indicator (letters get processed or treated).
'after' means one lot of letters go next to another.
'uranium' becomes 'U' (U is the chemical symbol for uranium).
'metal'+'it'='metalit'
'metalit' is an anagram of 'ltimate'.
'ltimate' after 'u' is 'ULTIMATE'.
(Other definitions for ultimate that I've seen before include "Best - last" , "Final or absolute" , "Utmost; last" , "Best or most extreme" , "Mutilate in final way" .)