Sign of hope in part of London led by artist (7)
I believe the answer is:
rainbow
'sign of hope' is the definition.
(eg the rainbow above Noah's Ark)
'in part of london led by artist' is the wordplay.
'part of london' becomes 'Bow' (area of East London).
'led by' is a charade indicator (letters next to each other).
'artist' becomes 'RA' (Royal Academician, member of Royal Academy of Arts).
'in'+'bow'='inbow'
'inbow' put after 'ra' is 'RAINBOW'.
(Other definitions for rainbow that I've seen before include "Multi-coloured arch" , "colours in the sky" , "Natural arch of colours" , "in different colours" , "heavenly sight" .)