To cap it, when rewritten the content is really awful (8)
I believe the answer is:
pathetic
'to cap it when rewritten the content is really awful' is the definition.
I can't tell whether this defines the answer.
'it when rewritten the content is really awful' is the wordplay.
'it' becomes 't' (abbreviation. e.g. in 'tis).
'when' becomes 'e' (I've seen this in other clues).
'rewritten' is an anagram indicator.
'the content' is an insertion indicator.
'is really awful' becomes 'pathic' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
't'+'e'='te'
'te' with letters rearranged gives 'et'.
'et' placed within 'pathic' is 'PATHETIC'.
Can you help me to learn more?
(Other definitions for pathetic that I've seen before include "Poor" , "Inspiring pity, contempt" , "Poignant or hopelessly inadequate" , "Arousing pity, miserably inadequate" , "Derisory" .)