Soft illumination leads to engagement (6)
I believe the answer is:
plight
'engagement' is the definition.
(thesaurus)
'soft illumination' is the wordplay.
'soft' becomes 'p' (musical abbreviation for 'piano').
'illumination' becomes 'light' (light is a kind of illumination).
'p'+'light'='PLIGHT'
'leads to' is the link.
(Other definitions for plight that I've seen before include "Unfortunate position" , "State" , "Alarming predicament" , "Promise - trouble" , "Dilemma" .)