The most common and most likely answer to this crossword clue is the 6 letter word SINGLE
I've seen this crossword clue in The Guardian
S
I
N
G
L
E
More clues leading to the result SINGLE
- Carol wants love first and last, being unattached
- Unique record run without partner
- One cared for obsessive
- One digesting short records in small car?
- One bashed in legs
- Run on your own?
- Rail ticket still on the shelf
- Carol, extremely likeable on her own
- Confess member’s short of $1,000, for the record
- Record run
Buddy explains!

The straight part
We know that "Rail ticket/still on the shelf" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case rail ticket/still on the shelf = single.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 SINGLE mean?
SINGLE noun- A 45 RPM vinyl record with one song on side A and one on side B.
- A popular song released and sold (on any format) nominally on its own though usually having at least one extra track.
- One who is not married or does not have a romantic partner.
- A score of one run.
- A hit in baseball where the batter advances to first base.
- A tile that has a different value (i.e. number of pips) at each end.
- A bill valued at $1.
- A one-way ticket.
- A score of one point, awarded when a kicked ball is dead within the non-kicking team's end zone or has exited that end zone. Officially known in the rules as a rouge.
- (chiefly in the plural) A game with one player on each side, as in tennis.
- One of the reeled filaments of silk, twisted without doubling to give them firmness.
- A handful of gleaned grain.
- A floating-point number having half the precision of a double-precision value.
- To identify or select one member of a group from the others; generally used with out, either to single out or to single (something) out.
- To get a hit that advances the batter exactly one base.
- To thin out.
- (of a horse) To take the irregular gait called singlefoot.
- To sequester; to withdraw; to retire.
- To take alone, or one by one.
- Not accompanied by anything else; one in number.
- Not divided in parts.
- Designed for the use of only one.
- Performed by one person, or one on each side.
- Not married or (in modern times) not involved in a romantic relationship without being married or not dating anyone exclusively.
- Having only one rank or row of petals.
- Simple and honest; sincere, without deceit.
- Uncompounded; pure; unmixed.
- Simple; foolish; weak; silly.