Mountainous area a beginner has left (5)
I believe the answer is:
tyrol
'mountainous area' is the definition.
(I've seen this before)
'a beginner has left' is the wordplay.
'a beginner' becomes 'tyro' (synonyms).
'has' is a charade indicator (letters next to each other).
'left' becomes 'l' (common abbreviation).
'tyro'+'l'='TYROL'
(Other definitions for tyrol that I've seen before include "Austrian Alpine state (English spelling)" , "Austrian province" , "mountain state" , "ski region" , "hills here" .)