____ algebra (6)
I believe the answer is:
linear
'algebra' is the definition.
(linear algebra is a kind of algebra)
This is the entire clue.
(Other definitions for linear that I've seen before include "Straight; sequential" , "In one dimension, I learn (anag.)" , "Long and narrow, of one dimension" , "Nailer (anag.)" , "Measured lengthwise" .)