Secures top place finally in decisive victory (9)
I believe the answer is:
landslide
'victory' is the definition.
(I've seen this before)
'secures top place finally in decisive' is the wordplay.
I cannot quite understand how this works, but
'top' could be 'lid' (lid is a kind of top) and 'lid' is present in the answer.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for landslide that I've seen before include "big majority" , "Movement at grass-roots level" , "Shifting of ground" , "Overwhelming success" , "Major earth movement" .)