Violently sticks egg inside cuckoo nest on tree (8)
I believe the answer is:
bayonets
'violently sticks' is the definition.
(stick can mean to stab or pierce)
'egg inside cuckoo nest on tree' is the wordplay.
'egg' becomes 'ay' (I can't justify this - if you can you should believe this answer much more).
'inside' is an insertion indicator.
'cuckoo' indicates an anagram (I've seen this in other clues).
'on' is a charade indicator (letters next to each other).
'tree' becomes 'bo tree' (bo tree is a kind of tree).
'nest' anagrammed gives 'nets'.
'nets' after 'bo' is 'bonets'.
'ay' going within 'bonets' is 'BAYONETS'.
(Other definitions for bayonets that I've seen before include "Daggers fixed to rifles" , "Knives fixed to the ends of rifles" .)