I’m sorry, exercise books seem to be about a total of eleven (8)
I believe the answer is:
penitent
'i'm sorry' is the definition.
(I've seen this before)
'exercise books seem to be about a total of eleven' is the wordplay.
I cannot quite see how this works, but
'exercise' could be 'pe' (Physical Education) and 'pe' is found within the answer.
'books' could be 'nt' (abbreviation for New Testament) and 'nt' is found within the answer.
The remaining letters 'nite' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for penitent that I've seen before include "Showing remorse" , "Repentant" , "Regretting one's wrongdoings" , "Teen pint (anag.)" , "He's sorry for his sins" .)