Nothing absorbing on skin is unique (9)
I believe the answer is:
nonpareil
'unique' is the definition.
(I've seen this before)
'nothing absorbing on skin' is the wordplay.
'nothing' becomes 'nil' (eg nil is zero in football).
'absorbing' means one lot of letters goes inside another.
'skin' becomes 'pare' (synonyms).
'on'+'pare'='onpare'
'nil' placed around 'onpare' is 'NONPAREIL'.
'is' is the link.
(Other definitions for nonpareil that I've seen before include "Unique type" , "ideal" , "Without equal or rival, from France" , "like none other" , "Iron panel (anag.)" .)