A penny for criminal in US (4)

I believe the answer is:

perp

'criminal in us' is the definition.
(short for perpetrator in US English)

'a penny' is the wordplay.
'a' becomes 'per' (eg 'one a day' means 'one per day').
'penny' becomes 'p' (short for pence).
'per'+'p'='PERP'

'for' acts as a link.

I've seen this clue in The Times.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.