Beginner has left mountainous area (5)
I believe the answer is:
tyrol
'mountainous area' is the definition.
(I've seen this before)
'beginner has left' is the wordplay.
'beginner' becomes 'tyro' (synonyms).
'has' means one lot of letters go next to another.
'left' becomes 'l' (common abbreviation).
'tyro'+'l'='TYROL'
(Other definitions for tyrol that I've seen before include "Mountainous state of western Austria" , "hills here" , "Picturesque mountain area in Austria, popular with skiers" , "mountainous area" , "Alpine district of Austria and Italy" .)