The first worker gets a quantity that's equivalent (10)
I believe the answer is:
tantamount
'that's equivalent' is the definition.
(synonyms)
'the first worker gets a quantity' is the wordplay.
'the first' becomes 't' (1st letter of 'the').
'worker' becomes 'ant' (worker is a type of ant).
'gets' means one lot of letters go next to another.
'a quantity' becomes 'amount' ('amount' can be a synonym of 'quantity').
't'+'ant'+'amount'='TANTAMOUNT'
(Other definitions for tantamount that I've seen before include "Equal in value" , "Equivalent in seriousness (to)" , "Virtually equivalent (to)" , "Equivalent in value (to)" .)