Archaeological find: group with cash prepared to support it (11)
I believe the answer is:
sarcophagus
'archaeological find' is the definition.
(eg an ancient Egyptian sarcophagus)
'group with cash prepared to support it' is the wordplay.
'with' means one lot of letters go next to another.
'prepared' indicates an anagram.
'to support' is a charade indicator (letters next to each other) (in a down clue, some letters hold others up).
'it' becomes 'sa' (old-fashioned abbreviation for sex appeal).
'group' put after 'cash' is 'cashgroup'.
'cashgroup' anagrammed gives 'rcophagus'.
'rcophagus' put after 'sa' is 'SARCOPHAGUS'.
(Other definitions for sarcophagus that I've seen before include "form of coffin" , "Stone coffin" , "Final box" .)