The most common and most likely answer to this crossword clue is the 7 letter word TARIFFS
I've seen this crossword clue in The Daily Telegraph
T
A
R
I
F
F
S
Buddy explains!

The straight part
We know that "duties" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case duties = tariffs.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does TARIFFS mean?
TARIFFS noun- A system of government-imposed duties levied on imported or exported goods; a list of such duties, or the duties themselves.
- A schedule of rates, fees or prices.
- A sentence determined according to a scale of standard penalties for certain categories of crime.