Observing the absence of a ring? (6)
I believe the answer is:
noting
'observing' is the definition.
('note' can be a synonym of 'observe')
'absence of a ring?' is the wordplay.
'absence of' becomes 'no'.
'a ring?' becomes 'ting' (I have seen 'Sharp ring ' mean 'ting' so perhaps 'ring' could also mean 'ting').
'no'+'ting'='NOTING'
'the' acts as a link.
(Other definitions for noting that I've seen before include "Recording in writing" , "Paying close attention to something" , "Making brief record of something" , "Observing and jotting down" , "Observing or taking down" .)