Girl's seasonal strain (5)
I believe the answer is:
carol
This clue is a double definition.
'girl's' is the first definition.
(woman's name)
'seasonal strain' is the second definition.
(strain can mean a piece of music)
(Other definitions for carol that I've seen before include "Joyful song - woman's name" , "Girl's name; sing" , "Female" , "Joyful song - girl's name" , "A traditional Christmas song or hymn" .)