Unusually early to bed (5)
I believe the answer is:
layer
'bed' is the definition.
(I know that bed can be written as layer)
'unusually early' is the wordplay.
'unusually' indicates an anagram.
'early' with letters rearranged gives 'LAYER'.
'to' acts as a link.
(Other definitions for layer that I've seen before include "Stratum; chicken" , "Single thickness, tier" , "Productive chicken" , "Thickness of material or earth - relay it" , "Single thickness and hen" .)