Sheep under tree in religious retreat (6)
I believe the answer is:
ashram
'religious retreat' is the definition.
(type of religious retreat in Asia)
'sheep under tree' is the wordplay.
'sheep' becomes 'ram' (male sheep).
'under' means one lot of letters go next to another (below, in a down clue).
'tree' becomes 'ash' (ash is a kind of tree).
'ram' put after 'ash' is 'ASHRAM'.
'in' acts as a link.
(Other definitions for ashram that I've seen before include "Place of religious retreat for Hindus" , "religious community" , "etreat" , "Indian religious retreat" , "Hindu place of religious learning located in a marsh" .)