Disorganised paralegal overlooking a complaint (8)
I believe the answer is:
pellagra
'complaint' is the definition.
(pellagra is a kind of health problem)
'disorganised paralegal overlooking a' is the wordplay.
'disorganised' indicates anagramming the letters.
'overlooking' suggests deleting specific letters.
'paralegal' with 'a' taken away is 'pralegal'.
'pralegal' is an anagram of 'PELLAGRA'.
(Other definitions for pellagra that I've seen before include "Wasting disease, caused by a Vitamin B deficiency" , "Itching" , "ill with this?" .)