Poor female swan on river steamship (9)
I believe the answer is:
penniless
'poor' is the definition.
(similar in meaning)
'female swan on river steamship' is the wordplay.
'female swan' becomes 'pen' (I've seen this before).
'on' means one lot of letters go next to another (in a down clue, letters appear on others).
'river' becomes 'nile' (Nile is an example).
'steamship' becomes 'ss' (nautical abbreviation).
'pen'+'nile'+'ss'='PENNILESS'
(Other definitions for penniless that I've seen before include "Not rich" , "Broke" , "Jack in New York" , "Skint, without a cent" , "Without money, not a cent" .)