Unhappy, coming across last of uneaten stuff on beach (4)
I believe the answer is:
sand
'stuff on beach' is the definition.
'sand' can be an answer for 'beach'. I am unsure of the 'stuff on' bit.
'unhappy coming across last of uneaten' is the wordplay.
'unhappy' becomes 'sad' (associated in meaning).
'coming across' means one lot of letters goes inside another.
'last of' suggests the final letters.
The final letter of 'uneaten' is 'n'.
'sad' enclosing 'n' is 'SAND'.
Can you help me to learn more?
(Other definitions for sand that I've seen before include "Desert grit" , "Fine stone particles" , "It's used to make glass" , "Loose grains" , "Beach grit" .)