Musical work firm accommodates once, right at the edges (8)
I believe the answer is:
concerto
'musical work' is the definition.
(concerto is a type of musical composition)
'firm accommodates once right at the edges' is the wordplay.
'firm' becomes 'co' (a firm is a company).
'accommodates' means one lot of letters goes inside another.
'at the edges' suggests removing the centre.
'right' with its centre removed is 'rt'.
'once'+'rt'='oncert'
'co' enclosing 'oncert' is 'CONCERTO'.
(Other definitions for concerto that I've seen before include "Composition for accompanied soloist" , "Work for orchestra and soloist(s)" , "Solo/orchestra piece" , "Orchestral composition" , "Musical composition" .)