Duck coming across large person wielding spadelike tool (9)

'duck' is the definition.
(I know that shoveller is a type of duck)

'across large person wielding spadelike tool' is the wordplay.
I cannot quite see how this works, but
'large' could be 'l' (eg in clothes sizes) and 'l' is located in the answer.
'tool' could be 'shovel' (shovel is a kind of tool) and 'shovel' is found within the answer.
The remaining letters 'er' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).

'coming' is the link.

Can you help me to learn more?