She can be heard at Christmas (5)
I believe the answer is:
carol
'christmas' is the definition.
Although both the answer and definition are singular nouns, I can't understand how one could define the other.
'she can be heard' is the wordplay.
'she' becomes 'Caro'.
'can be 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'
'at' is the link.
Can you help me to learn more?
(Other definitions for carol that I've seen before include "Song celebrating the birth of Jesus" , "A traditional Christmas song or hymn" , "See 1" , "Girl's name; sing" , "Canticle" .)