Small and delicate female in river, swept back (5)
I believe the answer is:
elfin
'small and delicate' is the definition.
(I've seen this before)
'female in river swept back' is the wordplay.
'female' becomes 'f' (abbreviation).
'in' means one lot of letters goes inside another.
'river' becomes 'nile' (Nile is an example).
'swept back' says the letters should be written backwards.
'f' put into 'nile' is 'nifle'.
'nifle' reversed gives 'ELFIN'.
(Other definitions for elfin that I've seen before include "Small and fragile" , "Mischievous sprite" , "Like a tiny fairy" , "Small, delicate, mischievous and attractive" , "Dainty" .)