Worker in firm produces piece of poetry (5)
I believe the answer is:
canto
'piece of poetry' is the definition.
(I've seen this before)
'worker in firm' is the wordplay.
'worker' becomes 'ant' (worker is a type of ant).
'in' means one lot of letters goes inside another.
'firm' becomes 'co' (a firm is a company).
'ant' put within 'co' is 'CANTO'.
'produces' acts as a link.
(Other definitions for canto that I've seen before include "Portion of poem" , "Major division of a long poem" , "Highest part in a piece of choral music -- act on (anag)" , "Poetic piece" , "Division of e.g. Dante's Inferno" .)