Name got changed a great deal (7)
I believe the answer is:
megaton
'a great deal' is the definition.
The answer and definition can be both quantities as well as being singular nouns.
Maybe there's an association between them I don't understand?
'name got changed' is the wordplay.
'changed' is an anagram indicator.
'name'+'got'='namegot'
'namegot' with letters rearranged gives 'MEGATON'.
Can you help me to learn more?
(Other definitions for megaton that I've seen before include "weight" , "Measure of explosive power - montage (anag)" , "it weighs a lot" , "Powerful explosive unit" , "Unit of explosive power" .)