Disorganised runners-up withdrawing names one after another (7)
I believe the answer is:
pursuer
'one after another' is the definition.
(I've seen this before)
'disorganised runners-up withdrawing names' is the wordplay.
'disorganised' is an anagram indicator.
'withdrawing' is a deletion indicator.
'names' becomes 'nn' (an abbreviation for name twice).
'runners'+'up'='runnersup'
'runnersup' with 'nn' taken out is 'ruersup'.
'ruersup' is an anagram of 'PURSUER'.
(Other definitions for pursuer that I've seen before include "One giving chase" , "stalker" , "He's hounding" , "One trying to catch another" , "One following" .)