Eat — but not seriously, we hear (6)
I believe the answer is:
ingest
'eat' is the definition.
(I know that eat is a more specific form of ingest)
'not seriously we hear' is the wordplay.
'not seriously' becomes 'in jest' (I've seen this in another clue).
'we hear' indicates a 'sounds like' (homophone) clue.
'injest' is a homophone of 'INGEST'.
'but' acts as a link.
(Other definitions for ingest that I've seen before include "Absorb - signet (anag)" , "Eat - gin set (anag)" , "Gets in (anag.)" , "Swallow, absorb" , "Scoff" .)