Female, one wearing dresses on expeditions (7)
I believe the answer is:
safaris
'expeditions' is the definition.
(I know this)
'female one wearing dresses' is the wordplay.
'female' becomes 'f' (abbreviation).
'one' becomes 'a' (a thing is one thing).
'wearing' indicates putting letters inside.
'dresses' becomes 'saris' (sari is a kind of dress).
'f'+'a'='fa'
'fa' going into 'saris' is 'SAFARIS'.
'on' acts as a link.
(Other definitions for safaris that I've seen before include "African trips" , "Expeditions" .)