Department helping to catch one against corruption (11)

'corruption' is the definition.
(I know that corruption can be written as depravation)

'department helping to catch one against' is the wordplay.
I cannot quite see how this works, but
'department' could be 'd' (abbreviation eg in MOD Ministry of Defence) and 'd' is located in the answer.
'one' could be 'o' (I've seen this in other clues) and 'o' is found in the answer.
'against' could be 'v' (abbreviation for 'versus') and 'v' is found in the answer.
This may be the basis of the clue (or it may be nonsense).

Can you help me to learn more?