Bedding female alien (5)
I believe the answer is:
sheet
'bedding' is the definition.
(as in a bed sheet)
'female alien' is the wordplay.
'female' becomes 'she' (I've seen this before).
'alien' becomes 'et' (extra terrestrial).
'she'+'et'='SHEET'
(Other definitions for sheet that I've seen before include "Piece of writing paper" , "Bedcover" , "leaf" , "Bed cover" , "Sail-rope on the bed?" .)