Worker left European stock (6)
I believe the answer is:
handle
'stock' is the definition.
(thesaurus)
'worker left european' is the wordplay.
'worker' becomes 'hand' (hand is a kind of worker).
'left' becomes 'l' (common abbreviation).
'european' becomes 'e' (abbreviation e.g. EU).
'hand'+'l'+'e'='HANDLE'
(Other definitions for handle that I've seen before include "Manage or deal with - in manual way?" , "Trade in" , "Part by which something is carried" , "Deal with; name (colloq.)" , "Treat" .)