Black one by Dotty (5)
I believe the answer is:
ebony
'black' is the definition.
(similar in meaning)
'one by dotty' is the wordplay.
'dotty' is an anagram indicator.
'one'+'by'='oneby'
'oneby' anagrammed gives 'EBONY'.
(Other definitions for ebony that I've seen before include "hard stuff" , "Heavy hard wood, usually black" , "Very dark brown" , "Hard wood used for black piano keys and in cabinetwork" , "Very dark black" .)