Under Scottish mountain take in first of heather (7)
I believe the answer is:
beneath
'under' is the definition.
(under means beneath or underneath)
'scottish mountain take in first of heather' is the wordplay.
'scottish mountain' becomes 'ben' (Scottish term for a peak, eg Ben Nevis).
'take in' becomes 'eat' (to eat is to take in food).
'first of heather' becomes 'h' (1st letter of 'heather').
'ben'+'eat'+'h'='BENEATH'
(Other definitions for beneath that I've seen before include "Directly under" , "At a lower place" , "Unbefitting" , "At a lower level (than)" , "Inferior to" .)