Something sustaining, perhaps, for the pianist (5)
I believe the answer is:
pedal
'pianist' is the definition.
Although both the answer and definition are singular nouns, I can't understand how they can define each other.
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for pedal that I've seen before include "Lever worked by foot" , "Plead for bike pusher" , "related to feet" , "Brake or clutch perhaps" , "One may be sustaining" .)