Hair goo! (3)
I believe the answer is:
gel
'hair goo' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for gel that I've seen before include "Come together, take shape (colloq.)" , "Posh female" , "Preparation used in setting hair" , "Congeal - hair dressing" , "Set, become firmer" .)