Let on about meat (6)
I believe the answer is:
reveal
'let on' is the definition.
(I know that let on can be written as reveal)
'about meat' is the wordplay.
'about' becomes 're' ('re' means regarding or about).
'meat' becomes 'veal' (veal is a kind of meat).
're'+'veal'='REVEAL'
(Other definitions for reveal that I've seen before include "Make known or visible" , "Expose or display" , "Remove cover to display" , "Leak" , "Make known, uncover and allow to be seen" .)