Mountains called evil at first (5)
I believe the answer is:
range
'mountains' is the definition.
(range of mountains)
'called evil at first' is the wordplay.
'called' becomes 'rang' (called on the phone).
'at first' says to take the initial letters.
The initial letter of 'evil' is 'e'.
'rang'+'e'='RANGE'
(Other definitions for range that I've seen before include "Series, of mountains perhaps" , "Extent; line of mountains" , "spectrum" , "Amplitude" , "Number of items in a series" .)