Each mum coming through carries beach things (9)
I believe the answer is:
seashells
'beach things' is the definition.
Although both the answer and definition are plural nouns, I cannot understand how one could define the other.
'each mum coming through carries' is the wordplay.
'each' becomes 'ea' (abbreviation).
'mum' becomes 'sh' (both can mean 'keep quiet').
'coming through' becomes 'sells' (I can't justify this - if you can you should give a lot more credence to this answer).
'carries' indicates putting letters inside.
'ea'+'sh'='eash'
'eash' placed inside 'sells' is 'SEASHELLS'.
Can you help me to learn more?
(Other definitions for seashells that I've seen before include "Coverings of marine organisms" , "''She sells ... on the seashore'' (tongue-twister)" , "Hard outer coverings of salt water molluscs" , "She might sell them on the seashore" , "Protective homes for salt water molluscs" .)