Unsuccessful person (4-3)
'unsuccessful person' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for also-ran that I've seen before include "Poor performer in race" , "Non-winning horse" , "Not placed among the leaders" , "One of the losers" , "Unplaced racehorse" .)
(Another definition for alsoran that I've seen is " failure?".)