See most of the soldiers retreating (5)
I believe the answer is:
sight
'see' is the definition.
(I know that detect is a is a more specific form of the action of see)
'most of the soldiers retreating' is the wordplay.
'most of' means to remove the last letter.
'soldiers' becomes 'gis' (GI is an informal term for a US soldier).
'retreating' says the letters should be written in reverse.
'the' with its last letter removed is 'th'.
'th'+'gis'='thgis'
'thgis' backwards is 'SIGHT'.
(Other definitions for sight that I've seen before include "Observe" , "object of especial interest" , "24" , "View" , "Notice" .)