Yearn for unmarried woman (4)
I believe the answer is:
miss
I believe this clue is a double definition.
'yearn for' is the first definition.
(I've seen this in another clue)
'unmarried woman' is the second definition.
(as opposed to Mrs)
(Other definitions for miss that I've seen before include "Don't hit" , "Fail to meet - girl" , "Teacher" , "failure" , "teacher's address" .)