Beaten regularly, a mount (4)
I believe the answer is:
etna
'mount' is the definition.
(Etna is an example)
'beaten regularly a' is the wordplay.
'regularly' indicates alternate letters (regularly take one letter, leave next etc.).
The alternating letters of 'beaten' are 'etn'.
'etn'+'a'='ETNA'
(Other definitions for etna that I've seen before include "Sicily's 15" , "It could erupt" , "A neat sort of volcano" , "Italian smoker" , "Threatening mountain" .)