Former President First Lady left in bed (9)
I believe the answer is:
roosevelt
'former president' is the definition.
(I've seen this before)
'first lady left in bed' is the wordplay.
'first lady' becomes 'eve' (first woman in the Bible).
'left' becomes 'L' (common abbreviation).
'in' means one lot of letters goes inside another.
'bed' becomes 'roost' (I've seen this before).
'eve'+'l'='evel'
'evel' placed into 'roost' is 'ROOSEVELT'.
(Other definitions for roosevelt that I've seen before include "former president" , "Name of two twentieth century US presidents" , "Surname of 26th and 32nd US presidents" , "Long-term leader" , "See president" .)