Linesmen producing copper during toss-up (6)

'linesmen' is the definition.
Both the answer and definition are plural nouns.
Perhaps there's an association between them I don't understand?

'copper during toss-up' is the wordplay.
'copper' becomes 'DI' (detective inspector, type of copper).
'during' indicates putting letters inside.
'up' indicates anagramming the letters (letters get chucked up).
'toss' is an anagram of 'osts'.
'di' going within 'osts' is 'ODISTS'.

'producing' is the link.

Can you help me to learn more?