Winding ascent on railway line (8)
I believe the answer is:
ancestry
'line' is the definition.
('ancestry' can be a synonym of 'line')
'winding ascent on railway' is the wordplay.
'winding' is an anagram indicator.
'on' means one lot of letters go next to another.
'railway' becomes 'ry' (abbreviation for railway).
'ascent' is an anagram of 'ancest'.
'ancest'+'ry'='ANCESTRY'
(Other definitions for ancestry that I've seen before include "Any crest (anag.)" , "Lineage" , "Person's ethnic descent" , "Family tree" , "race" .)