A warrior's outfit (7)
I believe the answer is:
panoply
'outfit' is the definition.
The answer and definition can be both groups as well as being singular nouns.
Perhaps there's a link between them I don't understand?
'a warrior's' is the wordplay.
I cannot really understand how this works, but
'a' could be 'an' and 'an' is found within the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for panoply that I've seen before include "Apply no mix to splendid array" , "Wide range" , "Impressive display" , "brilliant array" , "Having full equipment" .)