Pearl turned out less bright (5)
I believe the answer is:
paler
'less bright' is the definition.
(I've seen this in another clue)
'pearl turned out' is the wordplay.
'turned out' indicates anagramming the letters (turn out can mean to organise).
'pearl' is an anagram of 'PALER'.
(Other definitions for paler that I've seen before include "comparatively anaemic" , "Less colourful" , "Lighter in colour" , "rather sickly-looking" , "Less dark" .)