In little bits, railway business (8)
I believe the answer is:
industry
'business' is the definition.
(industry is a kind of business)
'in little bits railway' is the wordplay.
'little bits' becomes 'dust' (I am not sure about this - if you are sure you should believe this answer much more).
'railway' becomes 'ry' (abbreviation for railway).
'in'+'dust'+'ry'='INDUSTRY'
Can you help me to learn more?
(Other definitions for industry that I've seen before include "Diligence" , "Commercial enterprise, the making of goods, say" , "Craft" , "Hard work" , "Work (of manufacturing)" .)