Strangely iridescent rash (10)
I believe the answer is:
indiscreet
'rash' is the definition.
(thesaurus)
'strangely iridescent' is the wordplay.
'strangely' indicates an anagram.
'iridescent' anagrammed gives 'INDISCREET'.
(Other definitions for indiscreet that I've seen before include "Too ready to tell secrets" , "Injudicious (anag of 6, 9 and 23)" , "shameless" , "Ill-judged" , "Too ready to reveal secret things" .)