Stalls around a square in the hills (8)
I believe the answer is:
pennines
'the hills' is the definition.
Both the answer and definition are plural nouns.
Perhaps they are linked in a way I don't understand?
'stalls around a square' is the wordplay.
'stalls' becomes 'pens' (I've seen this before).
'around' means one lot of letters goes inside another.
'a square' becomes 'nine' (nine is a square number).
'pens' enclosing 'nine' is 'PENNINES'.
'in' acts as a link.
Can you help me to learn more?
(Other definitions for pennines that I've seen before include "English mountain range" , "chain of hills" , "Backbone of England" , "Range of hills in England" .)