Associate turned over hideaway to find stuff (8)
I believe the answer is:
material
'stuff' is the definition.
(I know that stuff can be written as material)
'associate turned over hideaway' is the wordplay.
'associate' becomes 'mate' (mate is a kind of associate).
'turned over' shows that the letters should be reversed in order.
'hideaway' becomes 'lair' (I've seen this in another clue).
'lair' in reverse letter order is 'rial'.
'mate'+'rial'='MATERIAL'
'to find' acts as a link.
(Other definitions for material that I've seen before include "of serious importance" , "it is of some significance" , "Felt, perhaps" , "Preoccupied with physical, rather than spiritual, substance" , "I am alert to find cloth or information" .)