Small and delicate female in river standing up (5)
I believe the answer is:
elfin
'small and delicate' is the definition.
(elfin means small or cute)
'female in river standing up' is the wordplay.
'female' becomes 'f' (abbreviation).
'in' is an insertion indicator.
'river' becomes 'nile' (Nile River is an example).
'standing up' is a reversal indicator (in a down clue up is reverse order).
'f' going within 'nile' is 'nifle'.
'nifle' back-to-front is 'ELFIN'.
(Other definitions for elfin that I've seen before include "Small, delicately-framed" , "Small, delicate, mischievous and attractive" , "Small and delicate like fairy" , "Pixie-like" , "Small, delicate and charming" .)