Fresh prey spotted up in the mountains (8)
I believe the answer is:
pyrenees
'the mountains' is the definition.
(I've seen this before)
'fresh prey spotted up' is the wordplay.
'fresh' is an anagram indicator (a fresh re-ordering of the letters).
'spotted' becomes 'seen' (I've seen this in another clue).
'up' says the letters should be written backwards (in down clue: letters go upwards).
'seen' reversed gives 'nees'.
'prey' with letters rearranged gives 'pyre'.
'pyre'+'nees'='PYRENEES'
'in' acts as a link.
(Other definitions for pyrenees that I've seen before include "Chain of mountains" , "Andorra in these mountains" , "Mountains between France and Spain" , "Mountain range between France and Spain" , "European mountains" .)