Exactly the right thing (4,3,6)
I believe the answer is:
just the ticket
'exactly the right thing' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for just the ticket that I've seen before include "Exactly what's needed" , "Minimum requirement for one travelling" , "Appropriate or desirable thing" , "Perfect!" , "first class?" .)