Go along with using guest ticket, in short, but don't let on, they say (6)
I believe the answer is:
comply
'go along' is the definition.
(I've seen this in another clue)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for comply that I've seen before include "Go along with" , "Agree - obey orders" , "Act in accordance with someone's rules, commands or wishes" , "Conform to rules" , "Yield to another's wishes or rules" .)