Presumed a large number read badly (5)
I believe the answer is:
dared
'presumed' is the definition.
Although both the answer and definition are past participle verbs, I cannot see how they can define each other.
'a large number read badly' is the wordplay.
'a large number' becomes 'd'.
'badly' indicates an anagram.
'read' with letters rearranged gives 'ared'.
'd'+'ared'='DARED'
Can you help me to learn more?
(Other definitions for dared that I've seen before include "Had the nerve to" , "Defied, challenged" , "Acted with courage - or dread?" , "Goaded" , "Challenged (to a deed)" .)