Base sent back American troops one's put in the rear (5)
I believe the answer is:
enema
'put in the rear' is the definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Perhaps there's a link between them I don't understand?
'base sent back american troops one's' is the wordplay.
'base' becomes 'e' (Euler's number - base of natural logarithms).
'sent back' says the letters should be written in reverse.
'american troops' becomes 'men' (both can mean soldiers. I am not sure about the 'american' bit.).
'one' becomes 'a' (a thing is one thing).
'men' back-to-front is 'nem'.
'e'+'nem'+'a'='ENEMA'
Can you help me to learn more?
(Other definitions for enema that I've seen before include "medicine to get you going" , "Bowel evacuator" , "The bottom line in medical treatment?" , "Suppository" , "Medical liquid introduced anally" .)