Thing stored by cosmetician on retirement (4)
I believe the answer is:
item
'thing' is the definition.
(I've seen this before)
'stored by cosmetician on retirement' is the wordplay.
'stored by' indicates a hidden word.
'on retirement' shows that the letters should be reversed in order.
'meti' can be found hidden inside 'cosmetician'.
'meti' in reverse letter order is 'ITEM'.
(Other definitions for item that I've seen before include "Separate object or unit" , "One thing among many" , "Part of a list" , "Whole individual unit" , "Bit of information" .)