City on the Chisholm Trail (4)
I believe the answer is:
enid
'city on the chisholm trail' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for enid that I've seen before include "Miss Blyton" , "- Blyton, children's writer" , "'... Blyton, children's author (4)'" , "& 18 Down Children's author" , "Geraint's loved one" .)