Son’s preparing potatoes? Excellent (8)
I believe the answer is:
smashing
'excellent' is the definition.
(thesaurus)
'son's preparing potatoes?' is the wordplay.
I cannot quite understand how this works, but
'son's' could be 's' and 's' is found within the answer.
'potatoes?' could be 'mash' (mashed potato) and 'mash' is found in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for smashing that I've seen before include "Great" , "2 [COOL] or 3 [DANDY] perhaps, possibly 20d [WICKED] or 22 [GEAR] !" , "Breaking things - super!" , "Wonderful" , "Excellent; breaking" .)