Right before four a disheartened lass sees opponents (6)
I believe the answer is:
rivals
'opponents' is the definition.
'right before four a disheartened lass' is the wordplay.
'right' becomes 'r' (common abbreviation).
'before' says to put letters next to each other.
'four' becomes 'iv' ('IV' can be a synonym of 'four').
'disheartened' says to hollow out the word (remove centre letters).
'lass' with its middle taken out is 'ls'.
'r'+'iv'+'a'+'ls'='RIVALS'
'sees' acts as a link.
(Other definitions for rivals that I've seen before include "Opposing contestants" , "Competitors, challengers" , "Competitors or adversaries" , "Opponents or competitors" , "Play by 1" .)