At home with Sean possibly or out to lunch (6)
I believe the answer is:
insane
'out to lunch' is the definition.
(not in command of one's mental faculties)
'at home with sean possibly' is the wordplay.
'at home' becomes 'in' ('in' can be similar in meaning to 'at home').
'with' says to put letters next to each other.
'possibly' indicates anagramming the letters.
'sean' anagrammed gives 'sane'.
'in'+'sane'='INSANE'
'or' is the link.
(Other definitions for insane that I've seen before include "Wild < cuckoo < cracked" , "reckless" , "Mad, irrational" , "off trolley" , "mad for love?" .)