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 "Annulus", "item to be fingered?", "Group operating illegally < call", "Circus space; surround", "Wedding band", "Hoop", "Circle; telephone", "resonant sound", "Marriage token" and "Phone; round".)