Case involving scam oddly undermining copper in charge (10)

'charge' is the definition.
(accusation is a kind of charge)

'case involving scam oddly undermining copper' is the wordplay.
'case' becomes 'action' (synonyms).
'involving' indicates putting letters inside.
'oddly' means one should take alternating letters (letters in the odd-numbered positions are used).
'undermining' means one lot of letters go next to another.
'copper' becomes 'cu' (chemical symbol).
The alternate letters of 'scam' are 'sa'.
'sa' after 'cu' is 'cusa'.
'action' going around 'cusa' is 'ACCUSATION'.

'in' acts as a link.