Disrespect shown by rough one blowing top is extremely serious (8)
I believe the answer is:
rudeness
'disrespect' is the definition.
(thesaurus)
'rough one blowing top is extremely serious' is the wordplay.
'rough' becomes 'rude' (similar in meaning).
'blowing top' means to remove the first letter.
'is extremely' suggests removing the centre (only the extremes of the word are used).
'serious' with its centre removed is 'ss'.
'one' with its first letter removed is 'ne'.
'rude'+'ne'+'ss'='RUDENESS'
'shown by' is the link.
(Other definitions for rudeness that I've seen before include "Impolite behaviour" , "Bad manners, lack of politeness" , "Vulgarity" , "Lip" , "Discourtesy" .)