Harassed magistrate disregards it though they're a massive celebrity (8)
I believe the answer is:
megastar
'celebrity' is the definition.
(I have seen 'Huge celebrity' mean 'megastar' so perhaps 'celebrity' could also mean 'megastar')
'harassed magistrate disregards it' is the wordplay.
'harassed' indicates anagramming the letters.
'disregards' suggests deleting specific letters.
'magistrate' with 'it' taken out is 'magsrate'.
'magsrate' is an anagram of 'MEGASTAR'.
'though they're a massive' is the link.
This may not be correct. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for megastar that I've seen before include "Great Sam (anag)" , "One v. famous" , "Huge celebrity" , "Very famous artist" , "A-list celeb" .)