Fool first, worker second (9)
I believe the answer is:
assistant
'second' is the definition.
(I've seen this before)
'fool first worker' is the wordplay.
'fool' becomes 'ass' (both can mean a stupid person).
'first' becomes 'ist' (ist resembles 1st).
'worker' becomes 'ant' (worker is a type of ant).
'ass'+'ist'+'ant'='ASSISTANT'
(Other definitions for assistant that I've seen before include "One helping" , "Aide, helper" , "help required?" , "Deputy, subordinate" , "Attendant, helper" .)