Union member on railway conservation (9)
I believe the answer is:
husbandry
'conservation' is the definition.
(thesaurus)
'union member on railway' is the wordplay.
'union member' becomes 'husband' (I can't justify this - if you can you should give a lot more credence to this answer).
'on' means one lot of letters go next to another (in a down clue, letters appear on others).
'railway' becomes 'ry' (abbreviation for railway).
'husband'+'ry'='HUSBANDRY'
Can you help me to learn more?
(Other definitions for husbandry that I've seen before include "farm management" , "farming task" , "Farm business" , "The care of crops and animals" , "Economy" .)