Gathered embarrassment visiting island upset daughter (9)
I believe the answer is:
assembled
'gathered' is the definition.
('assemble' can be a synonym of 'gather')
'embarrassment visiting island upset daughter' is the wordplay.
'embarrassment' becomes 'mess'.
'visiting' means one lot of letters goes inside another.
'island' becomes 'elba' (I've seen this before**).
'upset' says the letters should be written in reverse.
'daughter' becomes 'd'.
'mess' put into 'elba' is 'elbmessa'.
'elbmessa' in reverse letter order is 'assemble'.
'assemble'+'d'='ASSEMBLED'
(Other definitions for assembled that I've seen before include "Brought together" , "Gathered in one place or put together" , "Met up" , "Got together" , "Congregated, gathered" .)