Wanderlust (5,4)
I believe the answer is:
itchy feet
'wanderlust' is the definition.
(I know that wanderlust can be written as itchy feet)
This is the entire clue.
(Other definitions for itchy feet that I've seen before include "reason for leaving?" , "Restlessness, a desire to travel - or scratch?" , "Those with these have a strong impulse to travel" , "Strong desire to travel" , "They show a strong urge to travel" .)