Hairdo goo (3)
I believe the answer is:
gel
'hairdo goo' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for gel that I've seen before include "Hair treatment" , "Preparation used in setting hair" , "Leg it back to get some for your hair" , "Hair styling substance" , "Become jelly-like" .)