Retreat from area by marsh ground (6)
I believe the answer is:
ashram
'retreat' is the definition.
(type of religious retreat)
'area by marsh ground' is the wordplay.
'area' becomes 'a' (maths abbreviation).
'by' is a charade indicator (letters next to each other).
'ground' indicates an anagram ('grind' the letters into a new form).
'marsh' is an anagram of 'shram'.
'a'+'shram'='ASHRAM'
'from' is the link.
(Other definitions for ashram that I've seen before include "Hindu place of retreat" , "Indian religious retreat" , "etreat" , "Hindu place of religious learning located in a marsh" , "Hindu hermitage" .)