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 "Dial", "resonant sound", "group", "Circle that's square for boxers", "Make phone call", "Annulus", "Phone; circular band", "Circular, band of metal say", "Group operating illegally < call" and "Jewellery item".)