Break with trendy element of festival entertainment (8)
I believe the answer is:
infringe
'break' is the definition.
(infringing is a kind of breaking)
'with trendy element of festival entertainment' is the wordplay.
'with' says to put letters next to each other.
'trendy' becomes 'in'.
'element of festival entertainment' becomes 'fringe' (The Fringe at Edinburgh International Festival).
'in' next to 'fringe' is 'INFRINGE'.
(Other definitions for infringe that I've seen before include "Cross boundary" , "Break the rules" , "Encroach on (a right)" , "Violate" , "Break (rule)" .)