Linesmen producing copper during toss-up (6)

'linesmen' is the definition.
Both the definition and answer are plural nouns.
Maybe you can see an association between them that I don't see?

'copper during toss-up' is the wordplay.
'copper' becomes 'di' (detective inspector, type of copper).
'during' is an insertion indicator.
'up' is an anagram indicator.
'toss' is an anagram of 'osts'.
'di' inserted into 'osts' is 'ODISTS'.

'producing' is the link.

Can you help me to learn more?