Plea to dine among competitors (8)
I believe the answer is:
entreaty
'plea' is the definition.
(I've seen this before)
'dine among competitors' is the wordplay.
'dine' becomes 'eat' (I've seen this before).
'among' means one lot of letters goes inside another.
'competitors' becomes 'entry' (the people entered into a competition).
'eat' inserted inside 'entry' is 'ENTREATY'.
'to' is the link.
(Other definitions for entreaty that I've seen before include "suit" , "Teeny rat (anag.)" , "application for assistance" , "Earnest or urgent request" , "Earnest plea" .)