Runner-up? Nearer being a non-starter (5)
I believe the answer is:
loser
'runner-up?' is the definition.
(runner-up can mean anyone other than the winner)
'nearer being a non-starter' is the wordplay.
'nearer' becomes 'closer' (synonyms).
'being a non-starter' means to remove the first letter (the letter which starts the word is ignored).
'closer' with its initial letter removed is 'LOSER'.
(Other definitions for loser that I've seen before include "One failing regularly" , "sad type?" , "Defeated person" , "Opposite of winner" , "Unsuccessful person" .)