May be vital even if you can't play it (5)

I believe the answer is:

organ

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'it' is the definition.
The definition suggests a singular noun which matches the answer.

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(Other definitions for organ that I've seen before include "Pipe or reed instrument" , "Body part - musical instrument" , "Instrument - heart, for example" , "Wind instrument found in the body." , "specialist magazine" .)

I've seen this clue in the Evening Standard.

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