Worker eating cold ham left sauce (8)
I believe the answer is:
bechamel
'sauce' is the definition.
(bechamel is a kind of sauce)
'worker eating cold ham left' is the wordplay.
'worker' becomes 'bee' (I've seen this before).
'eating' indicates putting letters inside.
'cold' becomes 'c' (eg on taps).
'left' becomes 'l' (common abbreviation**).
'c'+'ham'='cham'
'bee' enclosing 'cham' is 'bechame'.
'bechame'+'l'='BECHAMEL'
(Other definitions for bechamel that I've seen before include "Thick white sauce" , "Mix of milk, butter and flour" , "milky sauce!" , "Milk thickened with a butter and flour roux" , "White sauce flavoured with onions and herbs" .)