Amuses amazingly, let's say (6)
I believe the answer is:
assume
'let's say' is the definition.
'assume' can be an answer for 'say' (thesaurus). I'm unsure of the 'let's' bit.
'amuses amazingly' is the wordplay.
'amazingly' is an anagram indicator.
'amuses' with letters rearranged gives 'ASSUME'.
Can you help me to learn more?
(Other definitions for assume that I've seen before include "Take for granted or agreed" , "Take to be the case" , "Adopt or take for granted" , "Take as true without proof" , "Accept as true without proof" .)