The amazing looking egg is cracked into it (10)
I believe the answer is:
staggering
'the amazing' is the definition.
(thesaurus)
'looking egg is cracked into it' is the wordplay.
'looking' becomes 'staring' (staring is a kind of looking).
'is cracked' indicates an anagram.
'into it' is an insertion indicator.
'egg' anagrammed gives 'gge'.
'staring' going around 'gge' is 'STAGGERING'.
(Other definitions for staggering that I've seen before include "The worse for drink" , "likely to fall over?" , "surprising" , "Astonishing" , "Amazing! - under the influence of drink?" .)