The most common and most likely answer to this crossword clue is the 7 letter word HAGGARD
I've seen this crossword clue in The Daily Telegraph
H
A
G
G
A
R
D
More clues leading to the result HAGGARD
- Rider’s careworn
- Rider of cadaverous appearance?
- She’s writer, looking run down
- Rider, evidently weary? Difficult to grip a horse
- Firm employing a horse and rider for example
- Set including outrageous gag is wasted
- Careworn writer
- A couple of grand in tough environment must be drawn
- Lean old woman taking up man’s dress?
- Tough gag to crack, admitted author
Buddy explains!

The straight part
We know that "Writer/tired and gaunt" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case writer/tired and gaunt = haggard.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 HAGGARD mean?
HAGGARD noun- A hunting bird captured as an adult.
- A young or untrained hawk or falcon.
- A fierce, intractable creature.
- A hag.
- Looking exhausted, worried, or poor in condition
- (of an animal) Wild or untamed
- (Isle of Man) A stackyard, an enclosure on a farm for stacking grain, hay, etc.