English setters one's perhaps seen on a farm (3)
I believe the answer is:
ewe
'english' is the definition.
(thesaurus)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for ewe that I've seen before include "Farm animal" , "Sheep found in sewer" , "21a [SHEEP]" , "Palindrome for a female sheep" , "Ram's partner?" .)