A large tree growing on mountain (6)
I believe the answer is:
alpine
'growing on mountain' is the definition.
'alpine' can be an answer for 'mountain' (I've seen this before). I'm not sure about the 'growing on' bit.
'a large tree' is the wordplay.
'large' becomes 'L' (eg in clothes sizes).
'tree' becomes 'pine' (pine is a kind of tree).
'a'+'l'+'pine'='ALPINE'
Can you help me to learn more?
(Other definitions for alpine that I've seen before include "Relating to a European mountain range" , "Native growing up in mountainous area" , "To do with great European mountains" , "Relating to high mountains" , "seen in rocky state?" .)