Illumination breaking down halts gig (8)
I believe the answer is:
gaslight
'illumination' is the definition.
(I've seen this before)
'breaking down halts gig' is the wordplay.
'breaking down' indicates an anagram.
'halts'+'gig'='haltsgig'
'haltsgig' is an anagram of 'GASLIGHT'.
(Other definitions for gaslight that I've seen before include "Old-fashioned illumination" , "Bergman film" , "Old guide in dark" , "source of illumination" , "Sort of illumination" .)