The most common and most likely answer to this crossword clue is the 7 letter word DURABLE
D
U
R
A
B
L
E
More clues leading to the result DURABLE
- Hardy expert supports Durham
- Enduring corruption of bad rule
- Strong conclusion of Angelou hidden by twisted Spanish poet?
- Persistent Egyptian god breaks twice as much, having no oxygen
- German artist on the rise, it’s said, having lasting quality
- Denim underwear, initially, right fit and hard-wearing
- Reforming could make Bluebeard be this strong
- Deserted old city on west-facing island is substantial…
- Long lasting rule, bad for a change
- Long lasting blade is manufactured around old city
Buddy explains!

The straight part
We know that "tough" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case tough = durable.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 DURABLE mean?
DURABLE noun- A durable thing, one useful over more than one period, especially a year.
- Able to resist wear, decay; lasting; enduring.