Unscrupulous opportunist makes fortune on railway (7)
I believe the answer is:
chancer
'unscrupulous opportunist' is the definition.
(I've seen this before)
'fortune on railway' is the wordplay.
I cannot really see how this works, but
'fortune' could be 'chance' (synonyms) and 'chance' is present in the answer.
'railway' could be 'r' (eg in Great Western Railway) and 'r' is present in the answer.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
'makes' acts as a link.
Can you help me to learn more?
(Other definitions for chancer that I've seen before include "Informally, one who tries his luck" , "One taking risks" , "Unscrupulous opportunist" , "opportunistic sort" , "Unscrupulous sort" .)