Long for a great day in bed (5)
I believe the answer is:
covet
'long for' is the definition.
(I've seen this before)
'a great day in bed' is the wordplay.
'a great day' becomes 've' (abbreviation for Victory in Europe Day).
'in' is an insertion indicator.
'bed' becomes 'cot' (cot is a kind of bed).
've' placed within 'cot' is 'COVET'.
(Other definitions for covet that I've seen before include "Be envious" , "Yearn to possess (an item owned by another)" , "Crave, long to possess" , "Hanker after" , "Envy" .)