Travel price OK, I'm off! (8)
I believe the answer is:
farewell
'i'm off' is the definition.
'travel price ok' is the wordplay.
'travel price' becomes 'fare' (as in a train fare).
'ok' becomes 'well' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'fare'+'well'='FAREWELL'
Can you help me to learn more?
(Other definitions for farewell that I've seen before include "Say goodbye" , "It may be said when 15" , "vale" , "Departure" , "Archaic goodbye - good luck" .)