The most common and most likely answer to this crossword clue is the 6 letter word CORRAL
I've seen this crossword clue in The Daily Telegraph
C
O
R
R
A
L
More clues leading to the result CORRAL
- Enclosure made of hard material sheltering rook
- Last of water filling pinkish kettle
- Beginning to regret filling pink pen
- Enclosure puts Rex in the pink
- End of letter written in pink pen
- Queen’s written in pink pen
- Well with round and large openings for pen
- Black stuff covering bishop’s pen
- Necklace material about right for a pound
- NCO losing Post Office pen
Buddy explains!

The straight part
We know that "pen" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case pen = corral.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 CORRAL mean?
CORRAL noun- An enclosure for livestock, especially a circular one.
- An enclosure or area to concentrate a dispersed group.
- A circle of wagons, either for the purpose of trapping livestock, or for defense.
- To capture or round up.
- To place inside of a corral.
- To make a circle of vehicles, as of wagons so as to form a corral.