Dash off a lot of material (4)
I believe the answer is:
bolt
'dash off' is the definition.
(I've seen this in another clue)
'a lot of material' is the wordplay.
I cannot quite see how this works, but
an anagram of 'lot' is 'olt' which is located in the answer.
A single letter 'b' remains which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for bolt that I've seen before include "Fasten - flee" , "for security reasons" , "Fasten shut; run away" , "Eat (one's food) quickly" , "playwright" .)