Tiring, I saw more failing with low grade (9)
I believe the answer is:
wearisome
'tiring' is the definition.
(thesaurus)
'i saw more failing with low grade' is the wordplay.
'failing with' indicates anagramming the letters.
'low grade' becomes 'e' (E is a low academic grade).
'i'+'saw'+'more'='isawmore'
'isawmore' mixed up with 'e' can make 'WEARISOME'.
(Other definitions for wearisome that I've seen before include "pestilential" , "Tedious, tiring" , "Vexatious" , "Trying" , "Boring" .)