Refusal of nurse to wear ring (6)
I believe the answer is:
denial
'refusal' is the definition.
(I've seen this before)
'nurse to wear ring' is the wordplay.
'nurse' becomes 'EN' (abbreviation for state-enrolled nurse).
'to wear' is an insertion indicator (to wear something is to be covered up by it).
'ring' becomes 'dial' (as in dialling a phone).
'en' inserted inside 'dial' is 'DENIAL'.
'of' acts as a link.
(Other definitions for denial that I've seen before include "Nailed (anag.)" , "Saying it isn't so" , "Refusal to acknowledge" , "Rejection or refusal" , "Daniel (anag.)" .)