Drifting, it's a danger to swimmers (3)
I believe the answer is:
net
'drifting' is the definition.
Both the answer and definition are adjectives. Perhaps they are linked in a way I don't understand?
'it's a danger to swimmers' is the wordplay.
I cannot quite see how this works, but
'it' could be 't' (abbreviation. e.g. in 'tis) and 't' is present in the answer.
The remaining letters 'ne' 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 net that I've seen before include "What separates court opponents" , "Open-meshed material (used for catching things?)" , "Catch -- after all deductions" , "After expenses" , "Mesh; profit" .)