Entry barrier to alter appearance, we hear (9)
I believe the answer is:
turnstile
'entry barrier' is the definition.
'turnstile' can be an answer for 'barrier' (turnstile is a kind of barrier). I'm unsure of the 'entry' bit.
'to alter appearance we hear' is the wordplay.
I cannot really understand how this works, but
'to' could be 'til' (I've seen this in another clue) and 'til' is found 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 turnstile that I've seen before include "Admission gate" , "Crowd-controlling gate, at entrance to sports-ground say" , "Pivoting gate, to football grounds say" , "Revolving gate" , "where spectators pass" .)