Triumphantly show off plate of health food (8)
I believe the answer is:
brandish
'triumphantly show off' is the definition.
(brandish can mean to show something off)
'plate of health food' is the wordplay.
'plate of health' becomes 'bran' (I can't justify this - if you can you should give a lot more credence to this answer).
'food' becomes 'dish' (dish is a kind of food).
'bran'+'dish'='BRANDISH'
(Other definitions for brandish that I've seen before include "Triumphantly draw attention to" , "Flaunt" , "parade" , "Exhibit aggressively" , "Wave as a threat" .)