Lowest charge by the German opportunist (6,6)

I believe the answer is:

bottom feeder

I'm a little stuck... Click here to teach me more about this clue!

'opportunist' is the definition.
(I know that bottom feeder is a type of opportunist)

'lowest charge by the german' is the wordplay.
'lowest' becomes 'bottom' (synonyms).
'charge by' becomes 'fee' (fee is a kind of charge. I am not sure about the 'by' bit.).
'the german' becomes 'der' ('the' in German).
'bottom'+'fee'+'der'='BOTTOM FEEDER'

Can you help me to learn more?

I've seen this clue in The Irish 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.