Meal is a source of discomfort (7)
I believe the answer is:
malaise
'discomfort' is the definition.
(I know that malaise is a type of discomfort)
'meal is a source of' is the wordplay.
'source of' indicates an anagram.
'meal'+'is'+'a'='mealisa'
'mealisa' is an anagram of 'MALAISE'.
(Other definitions for malaise that I've seen before include "Uneasy feeling" , "General feeling of discomfort" , "General feeling of unease or illness" , "sickness" , "depression" .)