British musical rejecting No.1 from Robert Plant (5)
I believe the answer is:
olive
'british musical rejecting no 1' is the definition.
I can't judge whether this definition defines the answer.
'from robert plant' is the wordplay.
'from' becomes 'o' (I've seen this in other clues).
'robert plant' becomes 'live' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'o'+'live'='OLIVE'
Can you help me to learn more?
(Other definitions for olive that I've seen before include "Girl's name - colour" , "Tree - shade of green" , "Fruit; Popeye's girlfriend" , "Greyish-green colour" , "Bitter fruit" .)