Artists in London location for colourful event (7)
I believe the answer is:
rainbow
'colourful event' is the definition.
(colourful weather phenomenon)
'artists in london location' is the wordplay.
'artists' becomes 'RA' (Royal Academy of the Arts).
'london location' becomes 'Bow' (Bow is a part of London).
'ra'+'in'+'bow'='RAINBOW'
'for' acts as a link.
(Other definitions for rainbow that I've seen before include "Colourful arc in the sky" , "Natural arch of colours" , "Heavenly phenomenon" , "illusory hope?" , "Iris was its goddess" .)