Arm or branch
I believe the answer is:
limb
This clue is a double definition.
'arm' is the first definition.
(I know that arm can be written as limb)
'branch' is the second definition.
(I know that branch can be written as limb)
(Other definitions for limb that I've seen before include "Part of body or branch of tree" , "as part of plane, say" , "Bough" , "Human's extension" , "Tentacle" .)