That is to say (6)
(Other definitions for namely that I've seen before include "to wit" , "Old especially" , "Videlicet" , "Viz" , "That is to say, specifically" .)
'that is to say' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for videlicet that I've seen before include "that is to say" , "in other words" , "to wit" , "Viz. in full, namely" .)
(Other definitions for to wit that I've seen before include "i.e." , "In other words" , "That is to say" , "specifically" , "Namely" .)