They aren't all named Giles! (7)
I believe the answer is:
farmers
'they' is the definition.
Both the answer and definition are plural nouns.
Maybe there's a link between them I don't understand?
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for farmers that I've seen before include "Agronomists" , "Cultivators of land" .)