Free ticket (4)
This clue could be a double definition.
'free' is the first definition.
(I've seen this before)
'ticket?' is the second definition.
Although both the answer and definition are singular nouns, I cannot understand how one could define the other.
Can you help me to learn more?
(Other definitions for single that I've seen before include "Short pop record" , "Individual - unmarried" , "One-way ticket" , "Not married, just the one" , "Concentrating on only one aim" .)
'free ticket' is the definition.
(a complimentary ticket)
This is all the clue.