Party with rector during the hours of darkness? Absolutely! (9)
I believe the answer is:
downright
'absolutely' is the definition.
(thesaurus)
'party with rector during the hours of darkness?' is the wordplay.
'party' becomes 'do' (do is a kind of party).
'with' becomes 'w' (abbreviation**).
'rector' becomes 'r'.
'during' indicates putting letters inside.
'the hours of darkness?' becomes 'night' (I've seen this before).
'r' placed within 'night' is 'nright'.
'do'+'w'+'nright'='DOWNRIGHT'
(Other definitions for downright that I've seen before include "Utter, arrant" , "rank" , "blunt" , "Frank" , "Out-and-out" .)