Shape altered a great deal (5)
I believe the answer is:
heaps
'a great deal' is the definition.
(I've seen this in another clue)
'shape altered' is the wordplay.
'altered' indicates anagramming the letters.
'shape' anagrammed gives 'HEAPS'.
(Other definitions for heaps that I've seen before include "Shape (anag) - lots" , "Mounds; lots" , "Lots (of piles?)" , "A large number; untidy mounds" , "Mounds, stacks" .)