The most common and most likely answer to this crossword clue is the 7 letter word CHRONIC
I've seen this crossword clue in The Times
C
H
R
O
N
I
C
More clues leading to the result CHRONIC
- Very serious man with stylish clothing
- Republican appearing in stylish pants
- Very bad lad enthralled by elegance
- Most of the historical account is deplorable
- Inveterate Romeo working in elegant environment
- Trendy — right-on at heart — yet enduring
- Zero resistance put up in elegant pants
- Redhead about to wear fashionable rubbish
- Long-lasting commitment at first by Archie, Veronica, with their hearts, moving ahead
- Awful and dangerous
Buddy explains!

The straight part
We know that "pants" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case pants = chronic.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 CHRONIC mean?
CHRONIC noun- Marijuana, typically of high quality.
- A condition of extended duration, either continuous or marked by frequent recurrence. Sometimes implies a condition which worsens with each recurrence, though that is not inherent in the term.
- A person who is chronic, such as a criminal reoffender or a person with chronic disease.
- Of a problem, that continues over an extended period of time.
- Prolonged or slow to heal.
- Of a person, suffering from an affliction that is prolonged or slow to heal.
- Inveterate or habitual.
- Very bad, awful.
- Extremely serious.
- Good, great; "wicked".