Range and location probably sensed, first of all (4)
I believe the answer is:
alps
'range' is the definition.
(mountain range)
'and location probably sensed first of all' is the wordplay.
'first of all' indicates taking the first letters.
The first letters of 'and location probably sensed' is 'ALPS'.
(Other definitions for alps that I've seen before include "High mountains" , "Swiss mountains" , "Slopes" , "Eur. mountain range" , "Mont Blanc is therein" .)