Dash along landing (10)
I believe the answer is:
splashdown
'landing' is the definition.
(splashdown is a kind of landing)
'dash along' is the wordplay.
'dash' becomes 'splash' (both can mean a small amount).
'along' becomes 'down' (synonyms).
'splash'+'down'='SPLASHDOWN'
(Other definitions for splashdown that I've seen before include "Landing of spacecraft on water" , "End of mission" , "A drop in the ocean" , "return of spacecraft" , "Spacecraft's landing at sea" .)