Thanks to a dunderhead, this means little (3)
I believe the answer is:
tad
'means little' is the definition.
'tad' can be an answer for 'little' (both can mean a small amount). I am not sure about the 'means' bit.
'thanks to a dunderhead' is the wordplay.
'thanks' becomes 'ta' (UK informal version of 'thank you').
'to a dunderhead' becomes 'd' (head letter of 'dunder').
'ta'+'d'='TAD'
'this' acts as a link.
Can you help me to learn more?
(Other definitions for tad that I've seen before include "little boy" , "A small amount (colloq.)" , "Little bit" , "Small amount or degree" , "Small bit" .)