Seat possibly lost around mid-October (5)
I believe the answer is:
stool
'seat' is the definition.
(stool is a kind of seat)
'possibly lost around mid-october' is the wordplay.
'possibly' indicates anagramming the letters.
'around' indicates putting letters inside.
'mid' indicates the central letters.
The middle of 'october' is 'o'.
'lost' anagrammed gives 'stol'.
'stol' placed around 'o' is 'STOOL'.
(Other definitions for stool that I've seen before include "Small seat" , "Backless chair" , "Three-legged backless seat" , "Armless seat" , "Seat without a back" .)