Heroic sailor, noble type, goes by car mostly (8)
I believe the answer is:
argonaut
'heroic sailor' is the definition.
(I've seen this before)
'by car mostly' is the wordplay.
'by' becomes 'argon' (I can't explain this - if you can you should give a lot more credence to this answer).
'car' becomes 'auto' (synonyms).
'mostly' means to remove the last letter.
'auto' with its final letter taken off is 'aut'.
'argon'+'aut'='ARGONAUT'
'noble type goes' acts as a link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for argonaut that I've seen before include "legendary sailor" , "Ancient mariner" , "Member of Jason's crew" , "Classical sailor" , "Companion of Jason" .)