Failing a test makes sense (5)
I believe the answer is:
taste
'sense' is the definition.
(taste is one of the five senses)
'failing a test' is the wordplay.
'failing' indicates anagramming the letters (a failed spelling of the word).
'a'+'test'='atest'
'atest' is an anagram of 'TASTE'.
'makes' is the link.
(Other definitions for taste that I've seen before include "style" , "The ability to discern good quality" , "Sample - discrimination" , "Nice distinction felt in the mouth" , "Small sample of food" .)