Long-lasting hairdo (4)
I believe the answer is:
perm
'long-lasting hairdo' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for perm that I've seen before include "Hairstyle treatment" , "make waves" , "Russian port; hairstyle" , "Hairdo - combination on football pools" , "Give a wave" .)