I teach PT badly. Sorry! (8)
I believe the answer is:
pathetic
'sorry' is the definition.
(thesaurus)
'i teach pt badly' is the wordplay.
'badly' indicates an anagram.
'i'+'teach'+'pt'='iteachpt'
'iteachpt' is an anagram of 'PATHETIC'.
(Other definitions for pathetic that I've seen before include "Touching and pitiful" , "Sad - hopeless" , "Inspiring pity, contempt" , "Hapless, miserable" , "Wretched" .)