Los Angeles hoodlum in lake (6)
I believe the answer is:
lagoon
'lake' is the definition.
(lagoon is a kind of lake)
'los angeles hoodlum' is the wordplay.
'los angeles' becomes 'la'.
'hoodlum' becomes 'goon' ('goon' can be a synonym of 'hoodlum').
'la'+'goon'='LAGOON'
'in' is the link.
(Other definitions for lagoon that I've seen before include "Water protected by a coral reef" , "Stretch of water inside coral reef or sandbank" , "Stretch of water within an atoll" , "Salt-water lake, often blue" , "Shallow salt-water lake" .)