Large dress fantastic in any event (10)
I believe the answer is:
regardless
'in any event' is the definition.
'large dress fantastic' is the wordplay.
'fantastic' indicates an anagram.
'large'+'dress'='largedress'
'largedress' with letters rearranged gives 'REGARDLESS'.
(Other definitions for regardless that I've seen before include "Lacking consideration" , "in spite of everything" , "Heeding no one - one of the 14 films" , "Indifferent - come what may" , "in any case" .)