Unfit due to a bad meal (4)
I believe the answer is:
lame
'unfit' is the definition.
(similar in meaning)
'a bad meal' is the wordplay.
'a bad' indicates an anagram.
'meal' is an anagram of 'LAME'.
'due to' is the link.
(Other definitions for lame that I've seen before include "Rubbish" , "Fabric interwoven with metal threads" , "Flimsy, as an excuse" , "Weak kind of excuse for halting walk" , "Hobbling" .)