Take a dip (4)
I believe the answer is:
swim
'take a dip' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for swim that I've seen before include "Go for a dip" , "To be in the .... is knowing what is going on" , "Float - feel dizzy" , "Crawl, say" , "Crawl, e.g." .)