Silver medallists seeing athlete dine (7,2)
I believe the answer is:
runners up
'silver medallists' is the definition.
(I've seen this before)
'athlete dine' is the wordplay.
'athlete' becomes 'runner' (type of athlete).
'dine' becomes 'sup' (synonyms).
'runner'+'sup'='RUNNERS-UP'
'seeing' is the link.
(Other definitions for runners up that I've seen before include "People scaling hills quickly?" , "who fail to get gold?" , "They almost won" , "a beanpole may welcome?" , "They take only seconds" .)