Get the round in — that which may be carried (4)
I believe the answer is:
load
'in that which may be carried' is the definition.
The definition and answer can be both quantities as well as being singular nouns.
Perhaps there's a link between them I don't understand?
'get the round' is the wordplay.
I cannot quite understand how this works, but
'round' could be 'o' (o is a circular letter) and 'o' is located in the answer.
The remaining letters 'lad' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for load that I've seen before include "A heavy burden" , "Burden, onus" , "pack" , "Great quantity" , "Goods carried by a large vehicle" .)