Long, pine (5)
I believe the answer is:
This clue is a double definition.
'long' is the first definition.
(I know that long can be written as yearn)
'pine' is the second definition.
(I know that pine can be written as yearn)
(Other definitions for yearn that I've seen before include "Feel desire" , "Desire strongly" , "Have an intense feeling of longing" , "Long (for something)" , "Pant - pine" .)