For superficial reasons they belittle senior boss regularly (5)
I believe the answer is:
snobs
'for superficial reasons they belittle' is the definition.
The definition suggests an adverb but the answer is not.
'senior boss regularly' is the wordplay.
'regularly' indicates alternate letters (regularly take one letter, leave next etc.).
'senior'+'boss'='seniorboss'
The alternating letters of 'seniorboss' are 'SNOBS'.
Can you help me to learn more?
(Other definitions for snobs that I've seen before include "Pretentious persons" , "have jobs at last" .)