Heat of battle at mountain height (6)
I believe the answer is:
warmth
'heat' is the definition.
(I know that warmth is a type of heat)
'battle at mountain height' is the wordplay.
'battle' becomes 'war' (armed conflict).
'at' is a charade indicator (letters next to each other).
'mountain' becomes 'mt'.
'height' becomes 'h' (abbreviation in geometry).
'war'+'mt'+'h'='WARMTH'
'of' is the link.
(Other definitions for warmth that I've seen before include "Possibly fire" , "Intensity of emotion" , "Affection, kindness; emotional intensity" , "Compassion" , "Sensation caused by heat" .)