Is punished: for a policeman it’s disastrous (4,2)

'disastrous' is the definition.
I don't know anything about this answer so I cannot tell whether this works.

'is punished for a policeman it's' is the wordplay.
'punished' indicates anagramming the letters.
'for' is a charade indicator (letters next to each other) (I've seen this in other clues).
'a policeman' becomes 'cop' (slang term).
'it' becomes ''t' (abbreviation. e.g. in 'tis).
'is' with letters rearranged gives 'si'.
'si' after 'cop' is 'copsi'.
'copsi'+'t'='COPS IT'

Can you help me to learn more?