Fuss also about dunderhead (2-2)
I believe the answer is:
to-do
'fuss' is the definition.
(I've seen this before)
'also about dunderhead' is the wordplay.
'also' becomes 'too' (synonyms).
'about' indicates putting letters inside.
'dunderhead' becomes 'd' (head letter of 'dunder').
'too' enclosing 'd' is 'TO-DO'.
(Other definitions for to-do that I've seen before include "Quarrel" , "Fuss or commotion" , "Kerfuffle" , "Spot of bother" , "Fuss and bother" .)