standing room; standing-only seat
Refers to a ticket or area where you stand to watch a performance, sports event, etc., rather than having a seat.
The standing-room tickets for the concert are already sold out.
You can still enjoy it even from the standing section.
自由席 is an unreserved seat, but you still get a seat; 立ち見席 means you stand.
Standard spelling with okurigana, clear and learner-friendly.
Kanji-only spelling, also common but slightly more formal or compact.
Compound of 立ち見 (standing and watching) + 席 (seat/place). The meaning is transparent from its parts.