Disclosure about lake (4)
I believe the answer is:
leak
'disclosure' is the definition.
(I know that leak is a type of disclosure)
'about lake' is the wordplay.
'about' indicates an anagram.
'lake' anagrammed gives 'LEAK'.
(Other definitions for leak that I've seen before include "Divulgation" , "Divulge" , "Ooze" , "Disclose unauthorised information" , "Let in water" .)