A Noel spent on one's own (5)
I believe the answer is:
alone
'on one's own' is the definition.
(I've seen this before)
'a noel spent' is the wordplay.
'spent' is an anagram indicator.
'noel' anagrammed gives 'lone'.
'a'+'lone'='ALONE'
(Other definitions for alone that I've seen before include "Without others present" , "Note of charges" , "Without others being involved" , "unique" , "without partner?" .)