Sign refurbished with lilac tint becomes brilliant (13)
I believe the answer is:
scintillating
'brilliant' is the definition.
(thesaurus)
'sign refurbished with lilac tint' is the wordplay.
'refurbished with' is an anagram indicator.
'lilac'+'tint'='lilactint'
'sign' mixed up with 'lilactint' can make 'SCINTILLATING'.
'becomes' acts as a link.
(Other definitions for scintillating that I've seen before include "Brilliantly clever" , "Sparkling" , "Brilliant - dazzling" .)