The most common and most likely answer to this crossword clue is the 4 plus 3 letter word PASS OUT
I've seen this crossword clue in The Daily Telegraph
P
A
S
S
O
U
T
More clues leading to the result PASS OUT
- Fool wears petulant expression to complete training
- Old man’s son dismissed issue
- Exeat for graduate
- Faint expression of petulance when idiot enters
- Faint moody expression about a case of shingles
- Complete the course and get dead drunk
- Entry document dismissed, as faint
- Complete training and faint
- What one on bottle might ultimately do X to complete training
- Graduate and get dead drunk
Buddy explains!

The straight part
We know that "Faint" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case faint = pass out.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 PASS OUT mean?
PASS OUT noun- A ticket (or similar) allowing a person to leave (a theatre etc) and subsequently re-enter