Rupees invested in a fake religious retreat (6)
I believe the answer is:
ashram
'religious retreat' is the definition.
(type of religious retreat in Asia)
'rupees invested in a fake' is the wordplay.
'rupees' becomes 'r' (abbreviation for rupees).
'invested in' means one lot of letters goes inside another.
'fake' becomes 'sham' (sham can mean fake or pretend).
'a'+'sham'='asham'
'r' going within 'asham' is 'ASHRAM'.
(Other definitions for ashram that I've seen before include "Hindu place of retreat" , "Hindu retreat house" , "Guru's community" , "Indian religious retreat" , "spiritual centre?" .)