Down amongst them is one of the shortest company releases (8)
I believe the answer is:
counties
'down amongst them is one of the shortest' is the definition.
(County Down is a county with a short name)
'company releases' is the wordplay.
'company' becomes 'co' (abbreviation).
'releases' becomes 'unties' (releases someone tied up).
'co'+'unties'='COUNTIES'
(Other definitions for counties that I've seen before include "administrative areas" , "Administrative divisions" .)