Yearn to curtail 2 (5)
I believe the answer is:
crave
'yearn' is the definition.
(thesaurus)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for crave that I've seen before include "Long for, desire" , "Beg; long for" , "Fairly sizeable" , "Hunger for" , "Powerfully desire" .)