Worker ate about noon (4)
I believe the answer is:
hand
'worker' is the definition.
(hand is a kind of worker)
'ate about noon' is the wordplay.
'ate' becomes 'had' (e.g. I had an ice cream).
'about' is an insertion indicator.
'noon' becomes 'n' (abbreviation).
'had' enclosing 'n' is 'HAND'.
(Other definitions for hand that I've seen before include "Worker; pointer" , "Worker - four inches - bunch of bananas" , "employee" , "Help < and applause" , "Round of applause" .)