Old worker snarfing seconds could be thus (5)
I believe the answer is:
obese
'could be thus' is the definition.
I can't tell whether this definition defines the answer.
'old worker snarfing seconds' is the wordplay.
I cannot really see how this works, but
'old' could be 'o' (common abbreviation eg in OE for Old English) and 'o' is found within the answer.
'seconds' could be 's' (abbreviation) and 's' is located in the answer.
'worker' could be 'bee' (a worker bee) and 'bee' is present in the leftover letters.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for obese that I've seen before include "in need of slimming down" , "Clinically overweight" , "Extremely overweight" , "Unusually fat" , "Plump" .)