Boat going over lagoons (5)
I believe the answer is:
sloop
'boat' is the definition.
(sloop is a kind of sailing vessel)
'going over lagoons' is the wordplay.
I cannot quite understand how this works, but
'over' could be 'o' (cricket abbreviation) and 'o' is found in the answer.
The remaining letters 'slop' 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 sloop that I've seen before include "something that's rigged" , "Type of sailing boat" , "craft" , "One-masted sailing ship" , "'----- John B', 1966 Beach Boys' hit" .)