Plant soldiers concealed outside entrance to camp (6)
I believe the answer is:
orchid
'plant' is the definition.
(orchid is a kind of plant)
'soldiers concealed outside entrance to camp' is the wordplay.
'soldiers' becomes 'OR' (Other Ranks).
'concealed' becomes 'hid' ('hide' can be a synonym of 'conceal').
'outside' indicates putting letters inside.
'entrance to' indicates taking the first letters.
The first letter of 'camp' is 'c'.
'or'+'hid'='orhid'
'orhid' going around 'c' is 'ORCHID'.
(Other definitions for orchid that I've seen before include "Showy tropical flower" , "Lady's slipper, for example" , "Blooming" , "Family of flowers with unusual shapes and beautiful colours" , "Exotic flower, often aromatic" .)