After economy with the truth mean to keep quiet (3,3)
I believe the answer is:
lie low
'keep quiet' is the definition.
(I've seen this before)
'after economy with the truth mean' is the wordplay.
'after' is a charade indicator (letters next to each other).
'economy with the truth' becomes 'lie'.
'mean' becomes 'low' (I've seen this before).
'lie' put next to 'low' is 'LIE LOW'.
'to' is the link.
(Other definitions for lie low that I've seen before include "Keep hidden" , "Use bottom bunk, perhaps" , "'Keep out of sight, avoid attention (3,3)'" , "Conceal oneself, don't be conspicuous" , "Avoid attracting notice" .)