Hydrate corrupt London police here? (3,4)
I believe the answer is:
the yard
'london police here?' is the definition.
(New Scotland Yard, HQ of the Metropolitan Police)
'hydrate corrupt' is the wordplay.
'corrupt' indicates anagramming the letters (a corrupted spelling of the word).
'hydrate' anagrammed gives 'THE YARD'.
(Other definitions for the yard that I've seen before include "Met base" , "London Metropolitan Police headquarters" .)