Racing driver who finished second several times (4)

I believe the answer is:
moss
'racing driver who finished' is the definition.
Although both the answer and definition are singular nouns, I don't understand how they can define each other.
'second several times' is the wordplay.
'second' becomes 'mo' (both are short periods of time).
'several times' becomes 'ss' (I can't justify this - if you can you should believe this answer much more).
'mo'+'ss'='MOSS'
Can you help me to learn more?
(Other definitions for moss that I've seen before include "Type of plant growing in damp places" , "Former racing driver" , "Plant forming most of my lawn!" , "evidence of neglect?" , "Low-growing plant" .)
