Soldiers in heap — confusing situation (6)
I believe the answer is:
morass
'confusing situation' is the definition.
(I've seen this in another clue)
'soldiers in heap' is the wordplay.
'soldiers' becomes 'OR' (military abbreviation for other ranks).
'in' means one lot of letters goes inside another.
'heap' becomes 'mass' (synonyms).
'or' put inside 'mass' is 'MORASS'.
(Other definitions for morass that I've seen before include "Bog; confused situation" , "Bog - situation hard to get out of" , "Bog or marsh" , "Tract of soft, wet ground" , "Area of marshy or swampy ground" .)