Running over before Saigon train's off (12)
I believe the answer is:
organisation
'running' is the definition.
('organisation' can be a synonym of 'running')
'over before saigon train's off' is the wordplay.
'over' becomes 'o' (cricket abbreviation**).
'before' is a charade indicator (letters next to each other).
'off' is an anagram indicator.
'saigon'+'train'='saigontrain'
'saigontrain' is an anagram of 'rganisation'.
'o'+'rganisation'='ORGANISATION'
(Other definitions for organisation that I've seen before include "Running" , "Systematic approach to tasks" , "concern" , "System" .)