Watercourse in the Skerries (3)
I believe the answer is:
esk
'watercourse' is the definition.
I know nothing about this answer so I can't judge whether this works.
'in the skerries' is the wordplay.
'in' indicates a hidden word.
'ESK' is hidden within 'the skerries'.
Can you help me to learn more?
(Other definitions for esk that I've seen before include "Scottish river" , "Northern river" , "River in the Borders" , "River flowing into Solway Firth" , "River in Dumfries" .)