E.g. tin soldiers in revolutionary set (7)
I believe the answer is:
element
'e' is the definition.
(thesaurus)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for element that I've seen before include "Ideal situation for someone" , "Constituent -- habitat" , "Operative part of an electric kettle" , "Basic chemical unit" , "For example, gold" .)