Everyone tour operator's welcoming on the wagon (5)
I believe the answer is:
tutti
'everyone' is the definition.
I can't judge whether this defines the answer.
'tour operator's welcoming on the wagon' is the wordplay.
'tour operator' becomes 'tui' (TUI is a travel and tourism company).
'welcoming' means one lot of letters goes inside another (in sense of 'inviting in').
'on the wagon' becomes 'TT' (short for teetotal).
'tui' enclosing 'tt' is 'TUTTI'.
Can you help me to learn more?
(Other definitions for tutti that I've seen before include "Every instrument to play" , "With all playing together (music)" , "- - -frutti" , "All instruments must play" , "Piece together" .)