One of the first things to put in a stocking (3)
I believe the answer is:
toe
'a stocking' is the definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Perhaps you can see an association between them that I don't see?
'one of the first things to put in' is the wordplay.
'one of' becomes 'o'.
'the first things' becomes 't' (est letter of 'things').
'to put' becomes 'e' (I can't explain this - if you can you should believe this answer much more).
'in' is an insertion indicator.
't'+'e'='te'
'o' placed inside 'te' is 'TOE'.
Can you help me to learn more?
(Other definitions for toe that I've seen before include "Lower end or tip" , "Pedal digit" , "Drive obliquely" , "Lower tip of something" , "low digit" .)