Gloomy character's blowing top over drugs and monstrosities (8)
I believe the answer is:
eyesores
'monstrosities' is the definition.
(eyesore can mean something horrible to look at)
'gloomy character's blowing top over drugs' is the wordplay.
'gloomy character's' becomes 'eeyore's' (character in the Winnie the Pooh books).
'blowing top' means to remove the first letter.
'over' indicates putting letters inside.
'drugs' becomes 'es' (E is a term for an ecstasy pill).
'eeyores' with its initial letter removed is 'eyores'.
'eyores' enclosing 'es' is 'EYESORES'.
'and' acts as a link.
(Other definitions for eyesores that I've seen before include "ugly looking things" , "They are offensive to see" , "Things that are ugly to look at, hurt optics" , "unattractive prospects" , "views people find offensive" .)