Admission, aka an admission fee was a fee paid which granter one access to a location.
In 2372, planning his own funeral, Quark decided to charge two slips of latinum per person to hear his eulogy, which was to be held in the holosuite. When Rom expressed uncertainty about doing so, Quark upped it to three. (DS9: "Body Parts")
In 2377, annoyed with Doctor Lewis Zimmerman's holographic pets, Leonard, a talking iguana, and Roy, a fly used for surveillance, The Doctor described Jupiter Station to Reginald Barclay as a three ring circus and suggested they charge admission. (VOY: "Life Line")