Sheepish soldiers with a leader of men (3)
I believe the answer is:
ram
'leader of men' is the definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Maybe you can see an association between them that I can't see?
'sheepish soldiers with a' is the wordplay.
'sheepish soldiers' becomes 'rm' (Royal Marines. I am not sure about the 'sheepish' bit.).
'with' means one lot of letters goes inside another.
'rm' placed around 'a' is 'RAM'.
Can you help me to learn more?
(Other definitions for ram that I've seen before include "An animal; forcibly crash into" , "barge" , "Drive hard" , "Tup" , "Aries is the Sign of the ..." .)