Like hippy's jacket without colour (4)
I believe the answer is:
ashy
'without colour' is the definition.
'like hippy's jacket' is the wordplay.
'like' becomes 'as'.
'jacket' says to hollow out the word (remove centre letters) (the letters worn by the word as a 'jacket' are use).
'hippy' with its centre taken out is 'hy'.
'as'+'hy'='ASHY'
(Other definitions for ashy that I've seen before include "Wan" , "Deathly pale" , "like Cinders" , "Leaden" , "evidence of recent fire" .)