Cut from expensive Toni and Guy with roots like Boris Johnson (7)
I believe the answer is:
etonian
'boris johnson' is the definition.
'cut from expensive toni and guy' is the wordplay.
'cut from' indicates a hidden word (the answer is cut out of the clue).
'ETONIAN' is hidden within 'expensive toni and guy'.
'with roots like' is the link.
This may not be right. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for etonian that I've seen before include "English student" , "Pupil at posh English school" , "Relating to one particular school" , "student in establishment?" , "One educated at famous public school" .)