Los Angeles thug in shallows (6)
I believe the answer is:
lagoon
'shallows' is the definition.
(I've seen this in another clue)
'los angeles thug' is the wordplay.
'los angeles' becomes 'LA' (abbreviation).
'thug' becomes 'goon' (synonyms).
'la'+'goon'='LAGOON'
'in' acts as a link.
(Other definitions for lagoon that I've seen before include "Coastal lake" , "Area inside atoll" , "Pool" , "Shallow seaside lake" , "Salt-water lake, often blue" .)