Beneath pet to be unfancied competitor (8)
I believe the answer is:
underdog
'be unfancied competitor' is the definition.
I can't judge whether this defines the answer.
'beneath pet' is the wordplay.
'beneath' becomes 'under' (I've seen this before).
'pet' becomes 'dog'.
'under'+'dog'='UNDERDOG'
'to' acts as a link.
Can you help me to learn more?
(Other definitions for underdog that I've seen before include "No drudge (anag.)" , "Less fancied competitor" , "One expected to lose" , "Competitor expected to lose" , "Contestant who's not expected to win" .)