Messy, agent eating chop (6)
I believe the answer is:
sloppy
'messy' is the definition.
(I've seen this before)
'agent eating chop' is the wordplay.
'agent' becomes 'spy' (spy is a kind of agent).
'eating' is an insertion indicator.
'chop' becomes 'lop' (I've seen this in other clues).
'spy' going around 'lop' is 'SLOPPY'.
(Other definitions for sloppy that I've seen before include "Lacking neatness and order" , "Slipshod" , "maudlin" , "Careless; watery" , "Excessively casual" .)