Harmless trap set back inside Scottish mountain (6)
I believe the answer is:
benign
'harmless' is the definition.
(associated in meaning)
'trap set back inside scottish mountain' is the wordplay.
'trap' becomes 'gin' (gin trap is a kind of animal trap).
'set back' says the letters should be written backwards.
'inside' indicates putting letters inside.
'scottish mountain' becomes 'ben' (Scottish term for a peak, eg Ben Nevis).
'gin' back-to-front is 'nig'.
'nig' placed inside 'ben' is 'BENIGN'.
(Other definitions for benign that I've seen before include "Kindly; not harmful" , "Liberal" , "sweet" , "Innocuous, not malignant" , "Favourable" .)