Where to buy piano music? (4)

I believe the answer is:

shop

I'm a little stuck... Click here to teach me more about this clue!

'buy piano music?' is the definition.
'shop' can be an answer for 'buy' (thesaurus). I'm unsure of the 'piano music?' bit.

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for shop that I've seen before include "business situation is to succeed!" , "Denounce; boutique" , "Make purchase; inform on (someone)" , "Store - workplace" , "Establishment for the sale of goods" .)

I've seen this clue in the Evening Standard.

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