Workers in mine find old spice (7)
I believe the answer is:
pimento
'spice' is the definition.
(thesaurus)
'workers in mine find old' is the wordplay.
'workers' becomes 'men' (man is a kind of worker).
'in' is an insertion indicator.
'mine' becomes 'pit' (down the pit).
'find' is a charade indicator (letters next to each other).
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'men' placed inside 'pit' is 'piment'.
'piment'+'o'='PIMENTO'
(Other definitions for pimento that I've seen before include "Sweet red pepper" , "Allspice - top mine (anag)" , "Plant" , "Type of pepper" , "Vegetable" .)