Firm retaining worker to produce a bit of poetry (5)
I believe the answer is:
canto
'a bit of poetry' is the definition.
'firm retaining worker' is the wordplay.
'firm' becomes 'co' (a firm is a company).
'retaining' means one lot of letters goes inside another.
'worker' becomes 'ant' (worker is a type of ant).
'co' enclosing 'ant' is 'CANTO'.
'to produce' acts as a link.
(Other definitions for canto that I've seen before include "Main division of long poem" , "Highest part in a piece of choral music -- act on (anag)" , "Section of a long poem" , "Each of sections into which long poem is divided" , "Division of e.g. Dante's Inferno" .)