Sweet shot with son in black hat? (10)
I believe the answer is:
gobstopper
'sweet' is the definition.
(type of large sweet)
'shot with son in black hat?' is the wordplay.
I cannot quite see how this works, but
'shot' could be 'go' (both can mean an attempt) and 'go' is found within the answer.
'son' could be 's' (genealogical abbreviation for son) and 's' is located in the answer.
'black' could be 'b' (as in pencil classifications) and 'b' is located in the answer.
'hat?' could be 'topper' (topper is a kind of hat) and 'topper' is found within the answer.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
(Other definitions for gobstopper that I've seen before include "Big sweet" , "Large, hard sweet to suck" , "Hard round sweet" , "Large, hard spherical sweet" .)