Bolan was one right into rainwear (4)
I believe the answer is:
marc
'bolan' is the definition.
I can't judge whether this definition defines the answer.
'one right into rainwear' is the wordplay.
'one right' becomes 'r' (common abbreviation).
'into' indicates putting letters inside.
'rainwear' becomes 'mac' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'r' inserted inside 'mac' is 'MARC'.
'was' acts as a link.
Can you help me to learn more?
(Other definitions for marc that I've seen before include "Brandy made from wine press residue" , "Type of eau-de-vie made from residue of grapes" , "Drink" , "Brandy distilled from grape residue" , "Grape refuse" .)