To remain in force, a guy in command on the parade ground (5,2,4)
I believe the answer is:
stand at ease
'command on the parade ground' is the definition.
'to remain in force a guy' is the wordplay.
'to remain in force' becomes 'stand' ('stand' can be a synonym of 'remain in force').
'guy' becomes 'tease' (I've seen this before).
'stand'+'a'+'tease'='STAND AT EASE'
'in' is the link.
(Other definitions for stand at ease that I've seen before include "Command to soldiers" , "order to relax" , "Instruction to soldiers - and sea state (anag)" , "Relax (on parade ground)" , "Command to troops" .)