The most common and most likely answer to this crossword clue is the 6 letter word USANCE
I've seen this crossword clue in Independent
U
S
A
N
C
E
More clues leading to the result USANCE
- University College going through moderate interest in Shakespeare
- African party in resort as before showing interest in literature
- American civil engineer after a new redemption period
- Country church accepts new time to pay foreign bills
- Proper attitude when time has passed for agreed period of exchange
- You and me can cast vote finally as is the custom
- Period of debt various ancestors would limit
- American church accepts an interest in redemption
- American corporation finally invested in wonderful time for payment
- Time awaiting payment nerve-racking at first, cause to get agitated about it?
Buddy explains!

The straight part
We know that "custom" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case custom = usance.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 USANCE mean?
USANCE noun- The length of time permitted for the payment of a bill of exchange.
- Use.
- Customary or habitual usage.
- The interest paid on a borrowed sum, usury.