Equipment includes new telephone (4)
I believe the answer is:
Here is my best explanation:
'telephone' is the definition.
('ring' can be a synonym of 'telephone')
'equipment includes new' is the subsidiary indication.
'equipment' becomes 'rig' (rig is a kind of equipment**).
'includes' indicates putting letters inside.
'new' becomes 'n'.
'rig' placed around 'n' is 'ring'.
(Other definitions for ring that I've seen before include "Wedding band", "Phone; circular band", "It's carried by Frodo", "'It's a square, strangely, for boxers (4)'", "Annulus", "Circular object - sound", "Surround; reverberate", "Phone; round", "Telephone - as bells do" and "Chime".)