Breach popular group around end of dinner (10)
I believe the answer is:
infraction
'breach' is the definition.
(a breach of the rules)
'popular group around end of dinner' is the wordplay.
'popular' becomes 'in' (something that's 'in' is fashionable).
'group' becomes 'faction' ().
'around' means one lot of letters goes inside another.
'end of' says to take the final letters.
The last letter of 'dinner' is 'r'.
'faction' going around 'r' is 'fraction'.
'in'+'fraction'='INFRACTION'
(Other definitions for infraction that I've seen before include "transgression" , "Breach of agreement" , "Violation of law" .)