Called 'Apennine' finally, mountain group (5)
I believe the answer is:
range
'mountain group' is the definition.
(I've seen this in another clue)
'called apennine finally' is the wordplay.
'called' becomes 'rang' (called on the phone).
'finally' indicates one should take the final letters.
The final letter of 'apennine' is 'e'.
'rang'+'e'='RANGE'
(Other definitions for range that I've seen before include "Walk for miles" , "sight" , "Wander freely" , "Scope (for target practice?)" , "area for stock" .)