Egg container in someone's trolley (4)
I believe the answer is:
nest
'egg container' is the definition.
(I've seen this in another clue)
'in someone's trolley' is the wordplay.
'in' says the answer is hidden in the clue.
'NEST' is hidden in the letters of 'someones trolley'.
(Other definitions for nest that I've seen before include "10 [HOUSE]" , "Home for a flier" , "Structure for laying eggs" , "Make a home (birds)" , "Snuggle in like bird" .)