Most delicate female realist upset (8)
I believe the answer is:
frailest
'most delicate' is the definition.
('frail' can be similar in meaning to 'delicate')
'female realist upset' is the wordplay.
'female' becomes 'f' (common abbreviation).
'upset' is an anagram indicator.
'realist' with letters rearranged gives 'railest'.
'f'+'railest'='FRAILEST'
(Other definitions for frailest that I've seen before include "Most delicate or weak" , "most fragile" .)