Shape revealed in crack (6,3)
I believe the answer is:
figure out
'crack' is the definition.
(thesaurus)
'shape revealed' is the wordplay.
'shape' becomes 'figure' (figure is a kind of shape).
'revealed' becomes 'out' (I've seen this in other clues).
'figure'+'out'='FIGURE OUT'
'in' acts as a link.
(Other definitions for figure out that I've seen before include "Reckon" , "understand?" , "Calculate - fathom" .)