Through which hitch-hiking is on the up and up? (5)
I believe the answer is:
lifts
'through which hitch-hiking is on' is the definition.
I can't tell whether this defines the answer.
'up and up?' is the wordplay.
'up' becomes 'lift' (up can mean to lift or raise).
'and' says to put letters next to each other.
'up?' becomes 's' (I am not sure about this - if you are sure you should believe this answer much more).
'lift'+'s'='LIFTS'
'the' acts as a link.
Can you help me to learn more?
(Other definitions for lifts that I've seen before include "Holds up" , "Picks up" , "Hoists" , "Elevates or elevators" , "They're elevators in America" .)