Leaf insect's colourful display (7)
I believe the answer is:
pageant
'colourful display' is the definition.
(I've seen this before)
'leaf insect's' is the wordplay.
'leaf' becomes 'page' (page is a kind of leaf).
'insect' becomes 'ant' (ant is a kind of insect).
'page'+'ant'='PAGEANT'
(Other definitions for pageant that I've seen before include "Dramatic performance" , "Spectacular parade" , "Spectacular ceremony" , "Elaborate procession on historical theme" , "Magnificent parade" .)