Egg can't go out of shape (7)
I believe the answer is:
octagon
'shape' is the definition.
(octagon is a kind of shape)
'egg can't go out' is the wordplay.
'egg' becomes 'o' (an 'o' resembles an egg).
'out' indicates anagramming the letters (out can mean wrong or inaccurate).
'cant'+'go'='cantgo'
'cantgo' with letters rearranged gives 'ctagon'.
'o'+'ctagon'='OCTAGON'
'of' acts as a link.
(Other definitions for octagon that I've seen before include "regular form" , "Geometric figure with eight sides" , "Eight-sided figure" , "plane figure" , "Figure of many sides" .)