Composer's one piece of work covered by Ireland retrospective (4,5)
I believe the answer is:
erik satie
'work covered by ireland retrospective' is the definition.
I don't know anything about this answer so I can't judge whether it can be defined by this definition.
'composer's one piece' is the wordplay.
I cannot quite see how this works, but
'one' could be 'er' (I've seen this in other clues) and 'er' is found in the answer.
'piece' could be 'k' (abbreviation for King) and 'k' is present in the answer.
'composer' could be 'satie' (French composer Erik Satie) and 'satie' is present in the answer.
A single letter 'i' remains which might be clued in a way I don't see.
This may be the basis of clue (or it may be nonsense).
'of' acts as a link.
Can you help me to learn more?