Sporting natter about new competitor (7)
I believe the answer is:
entrant
'competitor' is the definition.
(someone who has entered a competition)
'sporting natter about new' is the wordplay.
'sporting' indicates putting letters inside (inserted letters wear or 'sport' others).
'about' is an anagram indicator.
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'natter' is an anagram of 'entrat'.
'entrat' enclosing 'n' is 'ENTRANT'.
(Other definitions for entrant that I've seen before include "One going in for exam" , "Participant in competition" , "One taking part in a race or competition" , "Contestant; starter" , "Competitor, contestant" .)