Represent contest and former participants (5,3)
I believe the answer is:
stand for
'represent' is the definition.
(I know that represent can be written as stand for)
'contest and former participants' is the wordplay.
'participants' indicates a hidden word (some letters 'participating' in the clue).
'STAND FOR' is hidden in the letters of 'contest and former'.
(Other definitions for stand for that I've seen before include "Represent or tolerate" , "Represent while on feet?" , "champion" , "Signify" , "Mean" .)