Glamorous indefinable something unknown in railway (5)
I believe the answer is:
ritzy
'glamorous indefinable' is the definition.
I can't tell whether this defines the answer.
'something unknown in railway' is the wordplay.
'something' becomes 'it' (I've seen this in other clues).
'unknown' becomes 'z' (algebra).
'in' indicates putting letters inside.
'railway' becomes 'ry' (abbreviation for railway).
'it'+'z'='itz'
'itz' put within 'ry' is 'RITZY'.
Can you help me to learn more?
(Other definitions for ritzy that I've seen before include "Ostentatiously rich" , "Ostentatiously stylish" , "Ostentatiously opulent (sl.)" , "Richly elegant" , "Luxuriously opulent (slang)" .)