A king's taken in by charlatan's religious retreat (6)
I believe the answer is:
ashram
'religious retreat' is the definition.
(I've seen this before)
'a king's taken in by charlatan's' is the wordplay.
'king' becomes 'r' (r is abbreviation for rex).
'taken in by' indicates putting letters inside.
'charlatan' becomes 'sham'.
'r' put within 'sham' is 'shram'.
'a'+'shram'='ASHRAM'
(Other definitions for ashram that I've seen before include "Hindu retreat location" , "Retreat -- a marsh (anag)" , "Hindu religious retreat" , "Commune" , "Hindu place of retreat" .)