The most common and most likely answer to this crossword clue is the 4 letter word OWES
O
W
E
S
Buddy explains!
The straight part
We know that "Is in red" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case is in red = owes.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 OWES mean?
OWES verb- To be under an obligation to give something back to someone or to perform some action for someone.
- To have debt; to be in debt.