Fabulous support given to finish a railway (9)
I believe the answer is:
legendary
'fabulous' is the definition.
(I know that fabulous can be written as legendary)
'support given to finish a railway' is the wordplay.
'support given' becomes 'legend' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'to finish' is a charade indicator (letters next to each other) (some letters go after or 'finish' others).
'railway' becomes 'ry' (abbreviation for railway).
'legend'+'a'+'ry'='LEGENDARY'
Can you help me to learn more?
(Other definitions for legendary that I've seen before include "Relating to old or mythological tales" , "Mythical - very famous" , "notorious" , "From a fabulous traditional story" , "Mythical or fabled" .)