Hanker (for) (4)
'hanker for' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for yearn that I've seen before include "Have a great longing" , "Desire, want" , "Mark of injury" , "Have strong desire" , "wish" .)
(Other definitions for itch that I've seen before include "burn" , "Teasing desire" , "Prickle" , "Desire; irritation" , "Prickling" .)