Crossword Genius

Grass skirts with jumper in an estuary (10)

Ross

I believe the answer is:

sandhopper

I'm a little stuck... Click here to teach me more about this clue!

'jumper in an estuary' is the definition.
Although both the answer and definition are singular nouns, I don't understand how they can define each other.

'grass skirts with' is the wordplay.
'grass' becomes 'shopper' (I can't justify this - if you can you should believe this answer much more).
'skirts' means one lot of letters goes inside another (skirt can mean to go around).
'with' becomes 'and'.
'shopper' going around 'and' is 'SANDHOPPER'.

Can you help me to learn more?

(Other definitions for sandhopper that I've seen before include "jumper for the beach?" , "tiny crustacean" .)

I've seen this clue in The Times.
Want a hint initially instead of a full solution? Install my app