Railmen hammered copper for example (7)
I believe the answer is:
mineral
'copper for example' is the definition.
The definition and answer can be both substances as well as being singular nouns.
Perhaps there's an association between them I don't understand?
'railmen hammered' is the wordplay.
'hammered' is an anagram indicator (slang term for drunk).
'railmen' with letters rearranged gives 'MINERAL'.
Can you help me to learn more?
(Other definitions for mineral that I've seen before include "What drink is available in ground" , "Gypsum or magnesia, say" , "ore, possibly" , "Mined substance" , "E.g. bauxite, quartz" .)