Crystal read finally — aim with special procedure (8)
I believe the answer is:
dendrite
'crystal' is the definition.
(I know that dendrite is a type of crystal)
'read finally aim with special procedure' is the wordplay.
'finally' says to take the final letters.
'aim' becomes 'end' (both can mean a goal or purpose).
'with' says to put letters next to each other.
'special procedure' becomes 'rite' (eg rites in a church).
The last letter of 'read' is 'd'.
'd'+'end'+'rite'='DENDRITE'
(Other definitions for dendrite that I've seen before include "Crystalline tree-like structure" , "Dried net of the nerve fibre" .)