Lady often heard near Xmas (5)
I believe the answer is:
carol
'near xmas' is the definition.
Although both the answer and definition are singular nouns, I cannot see how they can define each other.
'lady often heard' is the wordplay.
'lady' becomes 'Caro'.
'often heard' becomes 'l' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'caro'+'l'='CAROL'
Can you help me to learn more?
(Other definitions for carol that I've seen before include "Coral (anag.)" , "sing happily" , "Religious song - girl's name" , "and 27: Waits" , "Joyful hymn" .)