Ignorant, like many soldiers about end of operation (10)
I believe the answer is:
uninformed
'ignorant' is the definition.
(I know that ignorant can be written as uninformed)
'like many soldiers about end of operation' is the wordplay.
'like many soldiers' becomes 'uniformed' (soldiers usually wear a uniform).
'about' means one lot of letters goes inside another.
'end of' suggests the final letters.
The last letter of 'operation' is 'n'.
'uniformed' going around 'n' is 'UNINFORMED'.
(Other definitions for uninformed that I've seen before include "Not knowledgeable" , "Missing dope" , "Lacking intelligence" , "in the dark" .)