Lowly soldiers embarrassed about rank (5)
I believe the answer is:
order
'rank' is the definition.
(I know that rank can be written as order)
'lowly soldiers embarrassed about' is the wordplay.
'lowly soldiers' becomes 'OR' (Other Ranks - low-ranking soldiers).
'embarrassed' becomes 'red' (someone may blush or go red when embarrassed).
'about' says the letters should be written backwards.
'red' backwards is 'der'.
'or'+'der'='ORDER'
(Other definitions for order that I've seen before include "goods supplied" , "Society of monks/nuns" , "Tidiness - that's a command" , "eg OBE" , "peace" .)