Spare kept in sack, poked nose in (8)
I believe the answer is:
bothered
'poked nose in' is the definition.
(both can mean interfered with)
'spare kept in sack' is the wordplay.
'spare' becomes 'other' (other can mean spare or alternative).
'kept in' is an insertion indicator.
'sack' becomes 'bed' ('in the sack' means 'in bed').
'other' placed into 'bed' is 'BOTHERED'.
(Other definitions for bothered that I've seen before include "` `Bewithched, ... and bewildered' '" , "Under stress" , "Disturbed" , "Made an effort -- put out" , "Was a pest" .)