Catch sight of rising summits (4)
I believe the answer is:
spot
'catch sight of' is the definition.
(to spot is to notice or catch sight of)
'rising summits' is the wordplay.
'rising' is a reversal indicator (going up in a down clue).
'summits' becomes 'tops' ('top' can be a synonym of 'summit').
'tops' back-to-front is 'SPOT'.
(Other definitions for spot that I've seen before include "Fix" , "small amount" , "make out" , "Discern - mark" , "Notice - stain - pick out" .)