Doctor Marten with no decoration (8)
I believe the answer is:
ornament
'decoration' is the definition.
(I know that decoration can be written as ornament)
'doctor marten with no' is the wordplay.
'doctor' is an anagram indicator.
'with' is a charade indicator (letters next to each other).
'marten' after 'no' is 'nomarten'.
'nomarten' is an anagram of 'ORNAMENT'.
(Other definitions for ornament that I've seen before include "Knick-knack" , "accessory" , "trill?" , "to dress up" , "Decorate" .)