Equipment including 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 including new' is the subsidiary indication.
'equipment' becomes 'rig' (rig is a kind of equipment**).
'including' means one lot of letters goes inside another.
'new' becomes 'n'.
'rig' enclosing 'n' is 'ring'.
(Other definitions for ring that I've seen before include "13's story of a 17", "Annulus", "Toll", "Band - call", "Circle, square for boxers", "Chime", "Circular band; call", "Frodo's burden (Tolkien)", "Surround; reverberate" and "Phone; circle".)