The most common and most likely answer to this crossword clue is the 5 letter word RALPH
I've seen this crossword clue in Financial Times
R
A
L
P
H
More clues leading to the result RALPH
- Man from Armagh regularly holding record
- Fellow engaged in moral philosophy
- Man perhaps writing half of the letters
- Chap’s moral philosophy greatly diminished
- One playing around with characters, a feature of moral philosophy
- Sacred flower for Richardson perhaps?
- Boy in river, sacred one
- He runs a large pub
- Man Mountain accommodated in Queen’s Hotel
Buddy explains!

The straight part
We know that "Boy" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case boy = ralph.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 RALPH mean?
RALPH verb- To vomit.
- A raven.