Mountain essential to national pride (3)
I believe the answer is:
alp
'mountain' is the definition.
(the Alps are a mountain range)
'essential to national pride' is the wordplay.
'essential to' indicates the answer is hidden within the clue (I've seen this in other clues).
'ALP' can be found hidden inside 'national pride'.
(Other definitions for alp that I've seen before include "One of a European mountain range" , "high point" , "Mont Blanc, for example" , "Mountain pasture" , "Swiss mountain" .)