Lurid key, gold, with dainty edges (5)
I believe the answer is:
gaudy
'lurid' is the definition.
(thesaurus)
'key gold with dainty edges' is the wordplay.
'key' becomes 'g' (musical key).
'gold' becomes 'Au' (Au is the chemical symbol for gold).
'with' means one lot of letters go next to another.
'edges' suggests removing the centre (I've seen 'edges of' mean this).
'dainty' with its centre removed is 'dy'.
'g'+'au'+'dy'='GAUDY'
(Other definitions for gaudy that I've seen before include "showy but tasteless" , "Vulgarly bright" , "Tastelessly bright" , "College feast" , "Tawdry" .)