Generally, a promotion includes rug with one-third off (2,1,4)
I believe the answer is:
as a rule
'generally' is the definition.
(I've seen this before)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for as a rule that I've seen before include "Usually, in the normal course" , "26 [NORMALLY]" , "Most of the time" , "how one might take a calibrated rod" , "Usually, in general" .)