Holy man bores posh couples on the next floor (8)
I believe the answer is:
upstairs
'on the next floor' is the definition.
(I've seen this before)
'holy man bores posh couples' is the wordplay.
'holy man' becomes 'st' (abbreviation for saint).
'bores' is an insertion indicator (bore can mean to drill into).
'posh' becomes 'u' (abbreviation for upper-class - opposite to non-U).
'couples' becomes 'pairs' ('pair' can be a synonym of 'couple').
'u'+'pairs'='upairs'
'st' put inside 'upairs' is 'UPSTAIRS'.
(Other definitions for upstairs that I've seen before include "in one's mind ..." , "On an upper floor" , "Above ground floor" , "on another level" , "at the next level" .)