Crack opening round top of pitcher (5)
I believe the answer is:
split
'crack' is the definition.
(I know that split is a type of crack)
'opening round top of pitcher' is the wordplay.
'opening' becomes 'slit' (slit is a kind of opening).
'round' means one lot of letters goes inside another.
'top of' says to take the initial letters.
The first letter of 'pitcher' is 'p'.
'slit' enclosing 'p' is 'SPLIT'.
(Other definitions for split that I've seen before include "Ripped" , "Divided" , "Adriatic port" , "Leave - crack" , "Divide, break apart" .)