The most common and most likely answer to this crossword clue is the 8 letter word DROP-OUT
I've seen this crossword clue in Independent
D
R
O
P
-
O
U
T
Buddy explains!

The straight part
We know that "Unsuccessful student/fresh start at Rugby" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case unsuccessful student/fresh start at rugby = drop-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 DROP-OUT mean?
DROP-OUT noun- Someone who has left an educational institution without completing the course
- Someone who has opted out of conventional society.
- One who suddenly leaves anything, or the act of doing so.
- The slot in the frame that accepts the axles of the wheels.
- A damaged portion of a tape or disk, causing a brief omission of audio, video, or data.
- Momentary loss of an electronic signal.
- A technique for regularizing a neural network by discarding a random subset of its units.