Complaint about a beam cast by firebrand (8)
I believe the answer is:
flambeau
'firebrand' is the definition.
(thesaurus)
'complaint about a beam cast by' is the wordplay.
'complaint' becomes 'flu' (flu is a kind of health problem).
'about' indicates putting letters inside.
'cast' is an anagram indicator (letters are dispersed or cast around).
'by' means one lot of letters go next to another.
'beam' is an anagram of 'ambe'.
'a' put after 'ambe' is 'ambea'.
'flu' going around 'ambea' is 'FLAMBEAU'.
(Other definitions for flambeau that I've seen before include "Burning torch" , "Old blazer" , "Torch; candlestick" , "One may be burning" , "Flaming torch" .)