Act like a couch potato, with "out" (3)
I believe the answer is:
veg
'act like a couch potato with out' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for veg that I've seen before include ""Meat and two __ "" , "Slob?" , "Food plants" , "Potatoes and cabbages etc" , "Eg, sprouts, parsnips" .)