Piece of cloth I found behind organ (5)
I believe the answer is:
lungi
'piece of cloth' is the definition.
(I've seen this before)
'i found behind organ' is the wordplay.
'found behind' means one lot of letters go next to another (some letters go behind others).
'organ' becomes 'lung' (lung is a kind of organ).
'i' after 'lung' is 'LUNGI'.
(Other definitions for lungi that I've seen before include "Eastern dress" , "worn piece of cloth" , "Indian man's loin-cloth" , "simple garment" , "Brightly coloured cloth worn in Asia as an ankle-length skirt" .)