Farm sector loses leader (5)
I believe the answer is:
ranch
'farm' is the definition.
(I know that ranch is a type of farm)
'sector loses leader' is the wordplay.
'sector' becomes 'branch' (branch can mean a sector or division).
'loses leader' means to remove the first letter.
'branch' with its initial letter taken away is 'RANCH'.
(Other definitions for ranch that I've seen before include "tear for a poet" , "American cattle farm" , "Cattle breeding farm" , "North American stock farm" , "US establishment for livestock" .)