Disinterested, alternatively, in bed (5)
I believe the answer is:
bored
'disinterested' is the definition.
(I've seen this in another clue)
'alternatively in bed' is the wordplay.
'alternatively' becomes 'or'.
'in' is an insertion indicator.
'or' placed inside 'bed' is 'BORED'.
(Other definitions for bored that I've seen before include "Filled with ennui" , "Wearied by tedium" , "Short of things to do, maybe" , "Drilled; wearied" , "Unstimulated" .)