Don, let's say (6)
I believe the answer is:
assume
I believe this is a triple definition!
'don' is the first definition.
(I've seen this before)
'let's' is the second definition.
(thesaurus)
'say' is the third definition.
(thesaurus)
(Other definitions for assume that I've seen before include "Take (responsibility)" , "Adopt falsely" , "Take for granted or agreed" , "Take (control)" , "Suppose - appropriate - feign - adopt" .)