Arm found in subsidiary office (6)
I believe the answer is:
branch
This clue is a double definition.
'arm' is the first definition.
(synonyms)
'subsidiary office' is the second definition.
(I've seen this in another clue)
'found in' is the link.
(Other definitions for branch that I've seen before include "regional office" , "local office" , "Part of tree/river" , "Division of some larger organisation" , "Offshoot or subdivision" .)