Single drum in ear, vibrating (9)
I believe the answer is:
unmarried
'single' is the definition.
(I know that single can be written as unmarried)
'drum in ear vibrating' is the wordplay.
'vibrating' indicates an anagram.
'drum'+'in'+'ear'='druminear'
'druminear' is an anagram of 'UNMARRIED'.
(Other definitions for unmarried that I've seen before include "Status of a bachelor" , "Single in terms of partnership" , "Not yet wed" .)