Something for hair: a thing unwanted there, prohibited, we understand (5,4)
I believe the answer is:
alice band
'something for hair' is the definition.
I know that 'hair' relates to this answer.
'a thing unwanted there prohibited we understand' is the wordplay.
I cannot quite see how this works, but
'a' could be 'an' and 'an' is present in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for alice band that I've seen before include "this on girl's head" , "Lock keeper" , "overhead arch" , "that contains shock?" , "may be found in the hair" .)