Great amount of ambiguity (3)
I believe the answer is:
big
'great' is the definition.
(I know that great can be written as big)
'amount of ambiguity' is the wordplay.
'amount of' indicates the answer is hidden within the clue (a certain amount of the clue).
'BIG' can be found hidden inside 'ambiguity'.
(Other definitions for big that I've seen before include "Important" , "Massive" , "Large; generous" , "London bell" , "oversized" .)