Delicacy brought first of tummy upsets (8)
I believe the answer is:
truffles
'delicacy' is the definition.
(truffles are a delicacy)
'first of tummy upsets' is the wordplay.
'first of tummy' becomes 't' (1st letter of 'tummy').
'upsets' becomes 'ruffles' (ruffle can mean to upset or disturb).
't'+'ruffles'='TRUFFLES'
'brought' is the link.
(Other definitions for truffles that I've seen before include "Richly flavoured fungi growing underground" , "Highly prized subterranean fungi" , "Rich-flavoured fungi growing underground" , "Highly-prized subterranean fungi" .)