Complex diagrams covering start of route for carnival (5,4)
I believe the answer is:
mardi gras
'carnival' is the definition.
(Mardi Gras is an example)
'complex diagrams covering start of route' is the wordplay.
'complex' indicates an anagram.
'covering' means one lot of letters goes inside another.
'start of' says to take the initial letters.
The initial letter of 'route' is 'r'.
'diagrams' is an anagram of 'madigras'.
'madigras' placed around 'r' is 'MARDI GRAS'.
'for' acts as a link.
(Other definitions for mardi gras that I've seen before include "Time for carnival" , "Shrove Tuesday carnival" , "festive occasion" , "The lead up to fast" , "Revelry celebrating Shrove Tuesday" .)