Not consistent or having a fixed pattern (8)
I believe the answer is:
variable
'not consistent or having a fixed pattern' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for variable that I've seen before include "Liable to change" , "can be changed" , "Changeable or inconstant" , "Fickle" , "Prone to change" .)