Icy mountain pass at the back of beyond (4)
I believe the answer is:
cold
'icy' is the definition.
('cold' can be similar in meaning to 'icy')
'mountain pass at the back of beyond' is the wordplay.
'mountain pass' becomes 'col' (col is a kind of mountain pass**).
'at the back of' indicates one should take the final letters (I've seen 'at the back' mean this).
The final letter of 'beyond' is 'd'.
'col'+'d'='COLD'
(Other definitions for cold that I've seen before include "Chilly; unemotional" , "Nippy" , "Lacking emotion" , "complaint" , "Lacking warmth" .)