High speed transport (8)
I believe the answer is:
aircraft
'high speed transport' is the definition.
'aircraft' can be an answer for 'transport' (aircraft is a kind of transport). I am not sure about the 'high speed' bit.
'high speed transport' is the wordplay.
'high speed' becomes 'air' (I can't explain this - if you can you should give a lot more credence to this answer).
'transport' becomes 'craft' (craft is a kind of transport).
'air'+'craft'='AIRCRAFT'
Can you help me to learn more?
(Other definitions for aircraft that I've seen before include "Eg, plane, helicopter, etc" , "Flying transport" , "Eg, seven four seven or Airbus" , "Airbus A380 or Boeing 777, say" , "I cart RAF? (Anag)" .)