Shelter in certain establishments (4)
I believe the answer is:
nest
'shelter' is the definition.
(I've seen this in another clue)
'in certain establishments' is the wordplay.
'in' indicates the answer is hidden within the clue.
'NEST' can be found hidden inside 'certain establishments'.
(Other definitions for nest that I've seen before include "Den" , "Place of retreat" , "Snuggle in like bird" , "Roost" , "breeding-ground" .)