Dreadful meal in time causes illness (7)
I believe the answer is:
ailment
'illness' is the definition.
(an ailment is an illness or health problem)
'dreadful meal in time' is the wordplay.
'dreadful' is an anagram indicator.
'time' becomes 't' (abbreviation).
'meal'+'in'='mealin'
'mealin' is an anagram of 'ailmen'.
'ailmen'+'t'='AILMENT'
'causes' acts as a link.
(Other definitions for ailment that I've seen before include "Tummy upset, for instance" , "Minor illness" , "Physical disorder" , "Malady" , "Complaint, affliction" .)