Phonograph part (4,3)
'phonograph part' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for arm that I've seen before include "Division of company" , "Ram into limb" , "Body part" , "What soldiers do" , "Shoulder-to-wrist member" .)
'phonograph part' is the definition.
('tone arm' is part of 'phonograph')
This is all the clue.
(Another definition for tone arm that I've seen is " Location of pick-up".)