Judge to be a letter badly set by silly me (6)
I believe the answer is:
esteem
'judge' is the definition.
(I know that esteem is a type of believe)
'a letter badly set by silly me' is the wordplay.
'a letter' becomes 'e' ().
'badly' indicates anagramming the letters.
'by' means one lot of letters go next to another.
'silly' indicates anagramming the letters.
'set' with letters rearranged gives 'ste'.
'me' is an anagram of 'em'.
'e'+'ste'+'em'='ESTEEM'
'to be' acts as a link.
(Other definitions for esteem that I've seen before include "High opinion, great respect" , "Venerate" , "Admiration, regard" , "Rate highly" , "Set a high value on" .)