Keep out of bed, maybe, for half a year (5)
I believe the answer is:
debar
'keep out' is the definition.
(to debar someone is to keep them out of something)
'bed maybe for half a year' is the wordplay.
'maybe' indicates anagramming the letters.
'for' says to put letters next to each other.
'half a' suggests halving the letters.
'year' cut in half is 'ar'.
'bed' with letters rearranged gives 'deb'.
'deb'+'ar'='DEBAR'
'of' is the link.
(Other definitions for debar that I've seen before include "Prohibit (from doing something)" , "Shut out, preclude" , "Large advert" , "Refuse to admit" , "Ban" .)