Group of soldiers finding young child on railway (8)
I believe the answer is:
infantry
'group of soldiers' is the definition.
(infantry means foot soldiers)
'young child on railway' is the wordplay.
'young child' becomes 'infant' (I've seen this before).
'on' is a charade indicator (letters next to each other) (in a down clue, letters appear on others).
'railway' becomes 'ry' (abbreviation for railway).
'infant'+'ry'='INFANTRY'
'finding' acts as a link.
(Other definitions for infantry that I've seen before include "Troops" , "Unmounted fighters" , "Men fighting" , "part of the army" , "Foot-soldiers" .)