Allow to do something to hair (6)
I believe the answer is:
permit
'allow' is the definition.
(I know that allow can be written as permit)
'something to hair' is the wordplay.
'something' becomes 'it' (I've seen this in other clues).
'to' is a charade indicator (letters next to each other) (I've seen this in other clues).
'hair' becomes 'perm' (perm is a kind of hair).
'it' after 'perm' is 'PERMIT'.
'to do' is the link.
This may not be correct. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for permit that I've seen before include "Allow, sanction" , "Allow - visa" , "Let; enabling document" , "Consent to, allow" , "Official document giving authorisation" .)