Harshly criticise judge along with strange self-important official (10)
I believe the answer is:
panjandrum
'self-important official' is the definition.
(person claiming great power)
'harshly criticise judge along with strange' is the wordplay.
'harshly criticise' becomes 'pan'.
'judge' becomes 'j' (abbreviation for judge).
'along with' becomes 'and'.
'strange' becomes 'rum' (synonyms).
'pan'+'j'+'and'+'rum'='PANJANDRUM'
(Other definitions for panjandrum that I've seen before include "pompous potentate" , "man of great influence" , "Big cheese" , "influential man" , "pompous official" .)