A clear note to twin girls (5)
I believe the answer is:
vivid
'a clear' is the definition.
(thesaurus)
'note to twin girls' is the wordplay.
'twin girls' means two replacements for 'girl'.
'note' becomes 'D' (musical note).
'to' means one lot of letters go next to another (I've seen this in other clues).
'girl' becomes 'vi' (short for Violet).
'girl' becomes 'vi' (short for Violet).
'vi'+'vi'='vivi'
'd' put after 'vivi' is 'VIVID'.
(Other definitions for vivid that I've seen before include "Strong and bright, colour perhaps" , "Fresh and bright" , "Presenting a clear and striking picture" , "Graphic" , "Brilliant" .)