To me, the top of my brain sounds like a thin layer of tissue (8)
I believe the answer is:
membrane
'a thin layer of tissue' is the definition.
(I've seen this in another clue)
'to me the top of my brain' is the wordplay.
I cannot quite see how this works, but
'me' is found in the answer.
'top' could be 'bra' (I've seen this in another clue) and 'bra' is present in the answer.
This explanation may well be incorrect...
'sounds like' is the link.
Can you help me to learn more?
(Other definitions for membrane that I've seen before include "cover" , "Cell lining" , "Thin sheet surrounding body parts" , "Thin sheet as a barrier" , "parchment skin" .)