Small and delicate female found in river flowing west (5)
I believe the answer is:
elfin
'small and delicate' is the definition.
(elfin means small or cute)
'female found in river flowing west' is the wordplay.
'female' becomes 'f' (abbreviation).
'found in' means one lot of letters goes inside another.
'river' becomes 'nile' (Nile River is an example).
'flowing west' says the letters should be written in reverse (written from right to left or 'east to west').
'f' placed within 'nile' is 'nifle'.
'nifle' in reverse letter order is 'ELFIN'.
(Other definitions for elfin that I've seen before include "little character" , "Dainty" , "Little, charming and naughty" , "Small and fragile" , "Small, mischievous and charming" .)