Went fast, but stopped short of the summit (4)
I believe the answer is:
sped
'went fast' is the definition.
(I've seen this before)
'stopped short of the summit' is the wordplay.
'short of' suggests deleting specific letters.
'the summit' becomes 'top' ('top' can be a synonym of 'summit').
'stopped' with 'top' taken out is 'SPED'.
'but' acts as a link.
(Other definitions for sped that I've seen before include "Rushed" , "Made haste" , "Moved quickly" , "Dashed" , "Moved fast" .)