Judgement right as teacher shows (5)
I believe the answer is:
taste
'judgement' is the definition.
(thesaurus)
'right as teacher shows' is the wordplay.
'shows' indicates the answer is hidden within the clue.
'TASTE' can be found hidden inside 'right as teacher'.
(Other definitions for taste that I've seen before include "Preference" , "Delicacy" , "Sample, savour" , "Sample orally" , "Brief sample; discernment" .)