Understatement no mature person prevaricates about (7)
I believe the answer is:
litotes
'understatement' is the definition.
(I've seen this before)
'person prevaricates about' is the wordplay.
'person' becomes 'tot' (tot is a kind of person).
'prevaricates' becomes 'lies' (I've seen this in another clue).
'about' is an insertion indicator.
'tot' placed inside 'lies' is 'LITOTES'.
'no mature' acts as a link.
This may not be correct. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for litotes that I've seen before include "in which not a little is a lot?" , "No exaggeration" , "Possibly, no small surprise" , "no overstatement" , "No little pain, say" .)