Part of a poem for worker in business (5)
I believe the answer is:
canto
'part of a poem' is the definition.
('canto' is part of 'poem')
'worker in business' is the wordplay.
'worker' becomes 'ant' (worker is a type of ant).
'in' means one lot of letters goes inside another.
'business' becomes 'co' (short for company).
'ant' inserted into 'co' is 'CANTO'.
'for' acts as a link.
(Other definitions for canto that I've seen before include "part of long poem" , "Section of a long poem" , "Major division of a long poem" , "Division of e.g. Dante's Inferno" , "Musical part" .)