Complaint about poor light leads to anger (9)
I believe the answer is:
displease
'to anger' is the definition.
(I've seen this before)
'complaint about poor light leads' is the wordplay.
'complaint' becomes 'disease' (I've seen this before).
'about' is an insertion indicator.
'leads' indicates taking the first letters.
The initial letters of 'poor light' is 'pl'.
'disease' enclosing 'pl' is 'DISPLEASE'.
(Other definitions for displease that I've seen before include "Nettle" , "Aggravate" , "Vex" , "Anger" , "Upset" .)