River shown in diagrams disrupted carnival (5,4)
I believe the answer is:
mardi gras
'carnival' is the definition.
(Mardi Gras is an example)
'river shown in diagrams disrupted' is the wordplay.
'river' becomes 'r'.
'shown in' indicates putting letters inside.
'disrupted' indicates an anagram.
'diagrams' anagrammed gives 'madigras'.
'r' inserted inside 'madigras' is 'MARDI GRAS'.
(Other definitions for mardi gras that I've seen before include "Time for carnival" , "Shrove Tuesday carnival" , "pre-Lent festival" , "festive occasion" , "Revelry celebrating Shrove Tuesday" .)