This competitor may be less than good after party (8)
I believe the answer is:
underdog
'this competitor may' is the definition.
The answer and definition can be both people as well as being singular nouns.
Maybe there's a link between them I don't understand?
'less than good after party' is the wordplay.
'less than' becomes 'under' (I've seen this in another clue).
'good' becomes 'g' (abbreviation).
'after' says to put letters next to each other.
'party' becomes 'do' (do is a kind of party).
'g' after 'do' is 'dog'.
'under'+'dog'='UNDERDOG'
'be' acts as a link.
Can you help me to learn more?
(Other definitions for underdog that I've seen before include "Unlikely Victor could be" , "One at a disadvantage" , "one not expected to win" , "Such is unlikely to succeed" , "Less fancied competitor" .)