Army soldiers ousting one from concealed position (5)
I believe the answer is:
horde
'army' is the definition.
(I've seen this before)
'soldiers ousting one from concealed position' is the wordplay.
I cannot really understand how this works, but
'soldiers' could be 'or' (Other Ranks) and 'or' is present in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for horde that I've seen before include "lots of people" , "Migratory tribe; army" , "Host" , "Many people" , "A moving crowd" .)