Lincoln seen by daughter possibly sleeping (4)
I believe the answer is:
abed
'possibly sleeping' is the definition.
(I've seen this before)
'lincoln seen by daughter' is the wordplay.
'lincoln' becomes 'abe' (Abraham Lincoln).
'seen by' means one lot of letters go next to another.
'daughter' becomes 'd' (genealogical abbreviation).
'abe'+'d'='ABED'
(Other definitions for abed that I've seen before include "sleeping? Apparently" , "Tucked up for the night" , "Sleeping under covers" , "Retired for the night" , "Bead (anag.)" .)