Clear oddly greasy wrinkles (6)
I believe the answer is:
ridges
'wrinkles' is the definition.
(ridges in a surface)
'clear oddly greasy' is the wordplay.
'clear' becomes 'rid' (synonyms).
'oddly' means one should take alternating letters (letters in the odd-numbered positions are used).
The alternating letters of 'greasy' are 'ges'.
'rid'+'ges'='RIDGES'
(Other definitions for ridges that I've seen before include "Strips either side of a ploughed furrow" , "Long narrow crests" , "Long raised strips" , "Long, narrow ranges of hilltops" , "long stretches high up" .)