Initiate is stripped and whipped until red (6)
I believe the answer is:
titian
'red' is the definition.
(I know that titian is a type of red)
'initiate is stripped and whipped' is the wordplay.
'is stripped' indicates the central letters (outside letters removed).
'and whipped' becomes 'tian' (I can't explain this - if you can you should give a lot more credence to this answer).
The middle of 'initiate' is 'ti'.
'ti'+'tian'='TITIAN'
'until' acts as a link.
I am not very happy about this link. It may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for titian that I've seen before include "Sixteenth century Venetian painter" , "Venetian fifteenth-sixteenth century painter" , "Italian Renaissance painter" , "Painter, noted for works with bright auburn hair" , "Italian painter; hair colour" .)